diff options
| author | christos <christos@NetBSD.org> | 2016-01-13 03:15:29 +0000 |
|---|---|---|
| committer | christos <christos@NetBSD.org> | 2016-01-13 03:15:29 +0000 |
| commit | eec8fc77c4e0eb79f8d0dce344cf1200ede12bfe (patch) | |
| tree | 0f84674d79cb0a0e6763dec26eb82850f961590f /external/gpl2/diffutils/dist/doc | |
| parent | ceb99fff3a910a1efe2f446026eaf8d0ed4086b2 (diff) | |
Import latest gpl2 diffutils
Diffstat (limited to 'external/gpl2/diffutils/dist/doc')
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/Makefile.am | 24 | ||||
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/Makefile.in | 359 | ||||
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/diagmeet.note | 71 | ||||
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/diff.info | 5084 | ||||
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/diff.texi | 4557 | ||||
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/fdl.texi | 404 | ||||
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/stamp-vti | 4 | ||||
| -rw-r--r-- | external/gpl2/diffutils/dist/doc/version.texi | 5 |
8 files changed, 10508 insertions, 0 deletions
diff --git a/external/gpl2/diffutils/dist/doc/Makefile.am b/external/gpl2/diffutils/dist/doc/Makefile.am new file mode 100644 index 00000000000..574fdab8705 --- /dev/null +++ b/external/gpl2/diffutils/dist/doc/Makefile.am @@ -0,0 +1,24 @@ +# Makefile for GNU diffutils documentation. + +# Copyright (C) 2001, 2002 Free Software Foundation, Inc. + +## This program is free software; you can redistribute it and/or modify +## it under the terms of the GNU General Public License as published by +## the Free Software Foundation; either version 2, or (at your option) +## any later version. + +## This program is distributed in the hope that it will be useful, +## but WITHOUT ANY WARRANTY; without even the implied warranty of +## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +## GNU General Public License for more details. + +## You should have received a copy of the GNU General Public License +## along with this program; if not, write to the Free Software Foundation, +## Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + +AM_MAKEINFOFLAGS = --no-split + +info_TEXINFOS = diff.texi +diff_TEXINFOS = fdl.texi + +EXTRA_DIST = diagmeet.note diff --git a/external/gpl2/diffutils/dist/doc/Makefile.in b/external/gpl2/diffutils/dist/doc/Makefile.in new file mode 100644 index 00000000000..408013d8e2b --- /dev/null +++ b/external/gpl2/diffutils/dist/doc/Makefile.in @@ -0,0 +1,359 @@ +# Makefile.in generated by automake 1.6 from Makefile.am. +# @configure_input@ + +# Copyright 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002 +# Free Software Foundation, Inc. +# This Makefile.in is free software; the Free Software Foundation +# gives unlimited permission to copy and/or distribute it, +# with or without modifications, as long as this notice is preserved. + +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY, to the extent permitted by law; without +# even the implied warranty of MERCHANTABILITY or FITNESS FOR A +# PARTICULAR PURPOSE. + +@SET_MAKE@ + +# Makefile for GNU diffutils documentation. + +# Copyright (C) 2001, 2002 Free Software Foundation, Inc. +SHELL = @SHELL@ + +srcdir = @srcdir@ +top_srcdir = @top_srcdir@ +VPATH = @srcdir@ +prefix = @prefix@ +exec_prefix = @exec_prefix@ + +bindir = @bindir@ +sbindir = @sbindir@ +libexecdir = @libexecdir@ +datadir = @datadir@ +sysconfdir = @sysconfdir@ +sharedstatedir = @sharedstatedir@ +localstatedir = @localstatedir@ +libdir = @libdir@ +infodir = @infodir@ +mandir = @mandir@ +includedir = @includedir@ +oldincludedir = /usr/include +pkgdatadir = $(datadir)/@PACKAGE@ +pkglibdir = $(libdir)/@PACKAGE@ +pkgincludedir = $(includedir)/@PACKAGE@ +top_builddir = .. + +ACLOCAL = @ACLOCAL@ +AUTOCONF = @AUTOCONF@ +AUTOMAKE = @AUTOMAKE@ +AUTOHEADER = @AUTOHEADER@ + +am__cd = CDPATH="$${ZSH_VERSION+.}$(PATH_SEPARATOR)" && cd +INSTALL = @INSTALL@ +INSTALL_PROGRAM = @INSTALL_PROGRAM@ +INSTALL_DATA = @INSTALL_DATA@ +install_sh_DATA = $(install_sh) -c -m 644 +install_sh_PROGRAM = $(install_sh) -c +INSTALL_SCRIPT = @INSTALL_SCRIPT@ +INSTALL_HEADER = $(INSTALL_DATA) +transform = @program_transform_name@ +NORMAL_INSTALL = : +PRE_INSTALL = : +POST_INSTALL = : +NORMAL_UNINSTALL = : +PRE_UNINSTALL = : +POST_UNINSTALL = : +host_alias = @host_alias@ +host_triplet = @host@ + +EXEEXT = @EXEEXT@ +OBJEXT = @OBJEXT@ +PATH_SEPARATOR = @PATH_SEPARATOR@ +AMTAR = @AMTAR@ +AWK = @AWK@ +BUILD_INCLUDED_LIBINTL = @BUILD_INCLUDED_LIBINTL@ +CATOBJEXT = @CATOBJEXT@ +CC = @CC@ +CPP = @CPP@ +DATADIRNAME = @DATADIRNAME@ +DEPDIR = @DEPDIR@ +GENCAT = @GENCAT@ +GLIBC21 = @GLIBC21@ +GMSGFMT = @GMSGFMT@ +HAVE_LIB = @HAVE_LIB@ +HELP2MAN = @HELP2MAN@ +INSTALL_STRIP_PROGRAM = @INSTALL_STRIP_PROGRAM@ +INSTOBJEXT = @INSTOBJEXT@ +INTLBISON = @INTLBISON@ +INTLLIBS = @INTLLIBS@ +INTLOBJS = @INTLOBJS@ +INTL_LIBTOOL_SUFFIX_PREFIX = @INTL_LIBTOOL_SUFFIX_PREFIX@ +LIB = @LIB@ +LIBICONV = @LIBICONV@ +LIBINTL = @LIBINTL@ +LIB_CLOCK_GETTIME = @LIB_CLOCK_GETTIME@ +LTLIB = @LTLIB@ +LTLIBICONV = @LTLIBICONV@ +LTLIBINTL = @LTLIBINTL@ +MKINSTALLDIRS = @MKINSTALLDIRS@ +PACKAGE = @PACKAGE@ +POSUB = @POSUB@ +PR_PROGRAM = @PR_PROGRAM@ +RANLIB = @RANLIB@ +STRIP = @STRIP@ +U = @U@ +USE_INCLUDED_LIBINTL = @USE_INCLUDED_LIBINTL@ +USE_NLS = @USE_NLS@ +VERSION = @VERSION@ +am__include = @am__include@ +am__quote = @am__quote@ +install_sh = @install_sh@ + +AM_MAKEINFOFLAGS = --no-split + +info_TEXINFOS = diff.texi +diff_TEXINFOS = fdl.texi + +EXTRA_DIST = diagmeet.note +subdir = doc +mkinstalldirs = $(SHELL) $(top_srcdir)/config/mkinstalldirs +CONFIG_HEADER = $(top_builddir)/config.h +CONFIG_CLEAN_FILES = +DIST_SOURCES = +TEXINFO_TEX = $(top_srcdir)/config/texinfo.tex +INFO_DEPS = diff.info +DVIS = diff.dvi +TEXINFOS = diff.texi +DIST_COMMON = $(diff_TEXINFOS) Makefile.am Makefile.in stamp-vti \ + version.texi +all: all-am + +.SUFFIXES: +.SUFFIXES: .dvi .info .ps .texi +$(srcdir)/Makefile.in: Makefile.am $(top_srcdir)/configure.ac $(ACLOCAL_M4) + cd $(top_srcdir) && \ + $(AUTOMAKE) --gnits doc/Makefile +Makefile: $(srcdir)/Makefile.in $(top_builddir)/config.status + cd $(top_builddir) && $(SHELL) ./config.status $(subdir)/$@ $(am__depfiles_maybe) + +$(srcdir)/version.texi: $(srcdir)/stamp-vti + @: +$(srcdir)/stamp-vti: diff.texi $(top_srcdir)/configure.ac + @(set `$(SHELL) $(top_srcdir)/config/mdate-sh $(srcdir)/diff.texi`; 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with no Invariant Sections, with the Front-Cover texts + being "A GNU Manual," and with the Back-Cover Texts as in (a) + below. A copy of the license is included in the section entitled + "GNU Free Documentation License." + + (a) The FSF's Back-Cover Text is: "You have freedom to copy and + modify this GNU Manual, like GNU software. Copies published by + the Free Software Foundation raise funds for GNU development." + +INFO-DIR-SECTION Individual utilities +START-INFO-DIR-ENTRY +* cmp: (diff)Invoking cmp. Compare 2 files byte by byte. +* diff: (diff)Invoking diff. Compare 2 files line by line. +* diff3: (diff)Invoking diff3. Compare 3 files line by line. +* patch: (diff)Invoking patch. Apply a patch to a file. +* sdiff: (diff)Invoking sdiff. Merge 2 files side-by-side. +END-INFO-DIR-ENTRY + +INFO-DIR-SECTION GNU packages +START-INFO-DIR-ENTRY +* Diff: (diff). Comparing and merging files. +END-INFO-DIR-ENTRY + + +File: diff.info, Node: Top, Next: Overview, Up: (dir) + +Comparing and Merging Files +*************************** + +This manual is for GNU Diffutils (version 2.8.1, 5 April 2002), and +documents the GNU `diff', `diff3', `sdiff', and `cmp' commands for +showing the differences between files and the GNU `patch' command for +using their output to update files. + + Copyright (C) 1992, 1993, 1994, 1998, 2001, 2002 Free Software +Foundation, Inc. + + Permission is granted to copy, distribute and/or modify this + document under the terms of the GNU Free Documentation License, + Version 1.1 or any later version published by the Free Software + Foundation; with no Invariant Sections, with the Front-Cover texts + being "A GNU Manual," and with the Back-Cover Texts as in (a) + below. A copy of the license is included in the section entitled + "GNU Free Documentation License." + + (a) The FSF's Back-Cover Text is: "You have freedom to copy and + modify this GNU Manual, like GNU software. Copies published by + the Free Software Foundation raise funds for GNU development." + +* Menu: + +* Overview:: Preliminary information. +* Comparison:: What file comparison means. + +* Output Formats:: Formats for two-way difference reports. +* Incomplete Lines:: Lines that lack trailing newlines. +* Comparing Directories:: Comparing files and directories. +* Adjusting Output:: Making `diff' output prettier. +* diff Performance:: Making `diff' smarter or faster. + +* Comparing Three Files:: Formats for three-way difference reports. +* diff3 Merging:: Merging from a common ancestor. + +* Interactive Merging:: Interactive merging with `sdiff'. + +* Merging with patch:: Using `patch' to change old files into new ones. +* Making Patches:: Tips for making and using patch distributions. + +* Invoking cmp:: Compare two files byte by byte. +* Invoking diff:: Compare two files line by line. +* Invoking diff3:: Compare three files line by line. +* Invoking patch:: Apply a diff file to an original. +* Invoking sdiff:: Side-by-side merge of file differences. + +* Standards conformance:: Conformance to the POSIX standard. +* Projects:: If you've found a bug or other shortcoming. + +* Copying This Manual:: How to make copies of this manual. +* Index:: Index. + + +File: diff.info, Node: Overview, Next: Comparison, Prev: Top, Up: Top + +Overview +******** + + Computer users often find occasion to ask how two files differ. +Perhaps one file is a newer version of the other file. Or maybe the +two files started out as identical copies but were changed by different +people. + + You can use the `diff' command to show differences between two +files, or each corresponding file in two directories. `diff' outputs +differences between files line by line in any of several formats, +selectable by command line options. This set of differences is often +called a "diff" or "patch". For files that are identical, `diff' +normally produces no output; for binary (non-text) files, `diff' +normally reports only that they are different. + + You can use the `cmp' command to show the byte and line numbers +where two files differ. `cmp' can also show all the bytes that differ +between the two files, side by side. A way to compare two files +character by character is the Emacs command `M-x compare-windows'. +*Note Other Window: (emacs)Other Window, for more information on that +command. + + You can use the `diff3' command to show differences among three +files. When two people have made independent changes to a common +original, `diff3' can report the differences between the original and +the two changed versions, and can produce a merged file that contains +both persons' changes together with warnings about conflicts. + + You can use the `sdiff' command to merge two files interactively. + + You can use the set of differences produced by `diff' to distribute +updates to text files (such as program source code) to other people. +This method is especially useful when the differences are small compared +to the complete files. Given `diff' output, you can use the `patch' +program to update, or "patch", a copy of the file. If you think of +`diff' as subtracting one file from another to produce their +difference, you can think of `patch' as adding the difference to one +file to reproduce the other. + + This manual first concentrates on making diffs, and later shows how +to use diffs to update files. + + GNU `diff' was written by Paul Eggert, Mike Haertel, David Hayes, +Richard Stallman, and Len Tower. Wayne Davison designed and +implemented the unified output format. The basic algorithm is described +in "An O(ND) Difference Algorithm and its Variations", Eugene W. Myers, +`Algorithmica' Vol. 1 No. 2, 1986, pp. 251-266; and in "A File +Comparison Program", Webb Miller and Eugene W. Myers, +`Software--Practice and Experience' Vol. 15 No. 11, 1985, pp. 1025-1040. +The algorithm was independently discovered as described in "Algorithms +for Approximate String Matching", E. Ukkonen, `Information and Control' +Vol. 64, 1985, pp. 100-118. + + GNU `diff3' was written by Randy Smith. GNU `sdiff' was written by +Thomas Lord. GNU `cmp' was written by Torbjorn Granlund and David +MacKenzie. + + `patch' was written mainly by Larry Wall and Paul Eggert; several +GNU enhancements were contributed by Wayne Davison and David MacKenzie. +Parts of this manual are adapted from a manual page written by Larry +Wall, with his permission. + + +File: diff.info, Node: Comparison, Next: Output Formats, Prev: Overview, Up: Top + +What Comparison Means +********************* + + There are several ways to think about the differences between two +files. One way to think of the differences is as a series of lines +that were deleted from, inserted in, or changed in one file to produce +the other file. `diff' compares two files line by line, finds groups of +lines that differ, and reports each group of differing lines. It can +report the differing lines in several formats, which have different +purposes. + + GNU `diff' can show whether files are different without detailing +the differences. It also provides ways to suppress certain kinds of +differences that are not important to you. Most commonly, such +differences are changes in the amount of white space between words or +lines. `diff' also provides ways to suppress differences in alphabetic +case or in lines that match a regular expression that you provide. +These options can accumulate; for example, you can ignore changes in +both white space and alphabetic case. + + Another way to think of the differences between two files is as a +sequence of pairs of bytes that can be either identical or different. +`cmp' reports the differences between two files byte by byte, instead +of line by line. As a result, it is often more useful than `diff' for +comparing binary files. For text files, `cmp' is useful mainly when +you want to know only whether two files are identical, or whether one +file is a prefix of the other. + + To illustrate the effect that considering changes byte by byte can +have compared with considering them line by line, think of what happens +if a single newline character is added to the beginning of a file. If +that file is then compared with an otherwise identical file that lacks +the newline at the beginning, `diff' will report that a blank line has +been added to the file, while `cmp' will report that almost every byte +of the two files differs. + + `diff3' normally compares three input files line by line, finds +groups of lines that differ, and reports each group of differing lines. +Its output is designed to make it easy to inspect two different sets of +changes to the same file. + +* Menu: + +* Hunks:: Groups of differing lines. +* White Space:: Suppressing differences in white space. +* Blank Lines:: Suppressing differences in blank lines. +* Case Folding:: Suppressing differences in alphabetic case. +* Specified Folding:: Suppressing differences that match regular expressions. +* Brief:: Summarizing which files are different. +* Binary:: Comparing binary files or forcing text comparisons. + + +File: diff.info, Node: Hunks, Next: White Space, Up: Comparison + +Hunks +===== + + When comparing two files, `diff' finds sequences of lines common to +both files, interspersed with groups of differing lines called "hunks". +Comparing two identical files yields one sequence of common lines and +no hunks, because no lines differ. Comparing two entirely different +files yields no common lines and one large hunk that contains all lines +of both files. In general, there are many ways to match up lines +between two given files. `diff' tries to minimize the total hunk size +by finding large sequences of common lines interspersed with small +hunks of differing lines. + + For example, suppose the file `F' contains the three lines `a', `b', +`c', and the file `G' contains the same three lines in reverse order +`c', `b', `a'. If `diff' finds the line `c' as common, then the command +`diff F G' produces this output: + + 1,2d0 + < a + < b + 3a2,3 + > b + > a + +But if `diff' notices the common line `b' instead, it produces this +output: + + 1c1 + < a + --- + > c + 3c3 + < c + --- + > a + +It is also possible to find `a' as the common line. `diff' does not +always find an optimal matching between the files; it takes shortcuts +to run faster. But its output is usually close to the shortest +possible. You can adjust this tradeoff with the `--minimal' option +(*note diff Performance::). + + +File: diff.info, Node: White Space, Next: Blank Lines, Prev: Hunks, Up: Comparison + +Suppressing Differences in Blank and Tab Spacing +================================================ + + The `-E' and `--ignore-tab-expansion' options ignore the distinction +between tabs and spaces on input. A tab is considered to be equivalent +to the number of spaces to the next tab stop. `diff' assumes that tab +stops are set every 8 print columns. + + The `-b' and `--ignore-space-change' options are stronger. They +ignore white space at line end, and consider all other sequences of one +or more white space characters to be equivalent. With these options, +`diff' considers the following two lines to be equivalent, where `$' +denotes the line end: + + Here lyeth muche rychnesse in lytell space. -- John Heywood$ + Here lyeth muche rychnesse in lytell space. -- John Heywood $ + + The `-w' and `--ignore-all-space' options are stronger still. They +ignore difference even if one line has white space where the other line +has none. "White space" characters include tab, newline, vertical tab, +form feed, carriage return, and space; some locales may define +additional characters to be white space. With these options, `diff' +considers the following two lines to be equivalent, where `$' denotes +the line end and `^M' denotes a carriage return: + + Here lyeth muche rychnesse in lytell space.-- John Heywood$ + He relyeth much erychnes seinly tells pace. --John Heywood ^M$ + + +File: diff.info, Node: Blank Lines, Next: Case Folding, Prev: White Space, Up: Comparison + +Suppressing Differences in Blank Lines +====================================== + + The `-B' and `--ignore-blank-lines' options ignore insertions or +deletions of blank lines. These options affect only lines that are +completely empty; they do not affect lines that look empty but contain +space or tab characters. With these options, for example, a file +containing + 1. A point is that which has no part. + + 2. A line is breadthless length. + -- Euclid, The Elements, I + +is considered identical to a file containing + 1. A point is that which has no part. + 2. A line is breadthless length. + + + -- Euclid, The Elements, I + + +File: diff.info, Node: Case Folding, Next: Specified Folding, Prev: Blank Lines, Up: Comparison + +Suppressing Case Differences +============================ + + GNU `diff' can treat lower case letters as equivalent to their upper +case counterparts, so that, for example, it considers `Funky Stuff', +`funky STUFF', and `fUNKy stuFf' to all be the same. To request this, +use the `-i' or `--ignore-case' option. + + +File: diff.info, Node: Specified Folding, Next: Brief, Prev: Case Folding, Up: Comparison + +Suppressing Lines Matching a Regular Expression +=============================================== + + To ignore insertions and deletions of lines that match a +`grep'-style regular expression, use the `-I REGEXP' or +`--ignore-matching-lines=REGEXP' option. You should escape regular +expressions that contain shell metacharacters to prevent the shell from +expanding them. For example, `diff -I '^[[:digit:]]'' ignores all +changes to lines beginning with a digit. + + However, `-I' only ignores the insertion or deletion of lines that +contain the regular expression if every changed line in the hunk--every +insertion and every deletion--matches the regular expression. In other +words, for each nonignorable change, `diff' prints the complete set of +changes in its vicinity, including the ignorable ones. + + You can specify more than one regular expression for lines to ignore +by using more than one `-I' option. `diff' tries to match each line +against each regular expression. + + +File: diff.info, Node: Brief, Next: Binary, Prev: Specified Folding, Up: Comparison + +Summarizing Which Files Differ +============================== + + When you only want to find out whether files are different, and you +don't care what the differences are, you can use the summary output +format. In this format, instead of showing the differences between the +files, `diff' simply reports whether files differ. The `-q' and +`--brief' options select this output format. + + This format is especially useful when comparing the contents of two +directories. It is also much faster than doing the normal line by line +comparisons, because `diff' can stop analyzing the files as soon as it +knows that there are any differences. + + You can also get a brief indication of whether two files differ by +using `cmp'. For files that are identical, `cmp' produces no output. +When the files differ, by default, `cmp' outputs the byte and line +number where the first difference occurs. You can use the `-s' option +to suppress that information, so that `cmp' produces no output and +reports whether the files differ using only its exit status (*note +Invoking cmp::). + + Unlike `diff', `cmp' cannot compare directories; it can only compare +two files. + + +File: diff.info, Node: Binary, Prev: Brief, Up: Comparison + +Binary Files and Forcing Text Comparisons +========================================= + + If `diff' thinks that either of the two files it is comparing is +binary (a non-text file), it normally treats that pair of files much as +if the summary output format had been selected (*note Brief::), and +reports only that the binary files are different. This is because line +by line comparisons are usually not meaningful for binary files. + + `diff' determines whether a file is text or binary by checking the +first few bytes in the file; the exact number of bytes is system +dependent, but it is typically several thousand. If every byte in that +part of the file is non-null, `diff' considers the file to be text; +otherwise it considers the file to be binary. + + Sometimes you might want to force `diff' to consider files to be +text. For example, you might be comparing text files that contain null +characters; `diff' would erroneously decide that those are non-text +files. Or you might be comparing documents that are in a format used +by a word processing system that uses null characters to indicate +special formatting. You can force `diff' to consider all files to be +text files, and compare them line by line, by using the `-a' or +`--text' option. If the files you compare using this option do not in +fact contain text, they will probably contain few newline characters, +and the `diff' output will consist of hunks showing differences between +long lines of whatever characters the files contain. + + You can also force `diff' to consider all files to be binary files, +and report only whether they differ (but not how). Use the `-q' or +`--brief' option for this. + + Differing binary files are considered to cause trouble because the +resulting `diff' output does not capture all the differences. This +trouble causes `diff' to exit with status 2. However, this trouble +cannot occur with the `--a' or `--text' option, or with the `-q' or +`--brief' option, as these options both cause `diff' to treat binary +files like text files. + + In operating systems that distinguish between text and binary files, +`diff' normally reads and writes all data as text. Use the `--binary' +option to force `diff' to read and write binary data instead. This +option has no effect on a POSIX-compliant system like GNU or +traditional Unix. However, many personal computer operating systems +represent the end of a line with a carriage return followed by a +newline. On such systems, `diff' normally ignores these carriage +returns on input and generates them at the end of each output line, but +with the `--binary' option `diff' treats each carriage return as just +another input character, and does not generate a carriage return at the +end of each output line. This can be useful when dealing with non-text +files that are meant to be interchanged with POSIX-compliant systems. + + The `--strip-trailing-cr' causes `diff' to treat input lines that +end in carriage return followed by newline as if they end in plain +newline. This can be useful when comparing text that is imperfectly +imported from many personal computer operating systems. This option +affects how lines are read, which in turn affects how they are compared +and output. + + If you want to compare two files byte by byte, you can use the `cmp' +program with the `-l' option to show the values of each differing byte +in the two files. With GNU `cmp', you can also use the `-b' option to +show the ASCII representation of those bytes. *Note Invoking cmp::, +for more information. + + If `diff3' thinks that any of the files it is comparing is binary (a +non-text file), it normally reports an error, because such comparisons +are usually not useful. `diff3' uses the same test as `diff' to decide +whether a file is binary. As with `diff', if the input files contain a +few non-text bytes but otherwise are like text files, you can force +`diff3' to consider all files to be text files and compare them line by +line by using the `-a' or `--text' options. + + +File: diff.info, Node: Output Formats, Next: Incomplete Lines, Prev: Comparison, Up: Top + +`diff' Output Formats +********************* + + `diff' has several mutually exclusive options for output format. +The following sections describe each format, illustrating how `diff' +reports the differences between two sample input files. + +* Menu: + +* Sample diff Input:: Sample `diff' input files for examples. +* Normal:: Showing differences without surrounding text. +* Context:: Showing differences with the surrounding text. +* Side by Side:: Showing differences in two columns. +* Scripts:: Generating scripts for other programs. +* If-then-else:: Merging files with if-then-else. + + +File: diff.info, Node: Sample diff Input, Next: Normal, Up: Output Formats + +Two Sample Input Files +====================== + + Here are two sample files that we will use in numerous examples to +illustrate the output of `diff' and how various options can change it. + + This is the file `lao': + + The Way that can be told of is not the eternal Way; + The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; + The Named is the mother of all things. + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + so we may see their outcome. + The two are the same, + But after they are produced, + they have different names. + + This is the file `tzu': + + The Nameless is the origin of Heaven and Earth; + The named is the mother of all things. + + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + so we may see their outcome. + The two are the same, + But after they are produced, + they have different names. + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! + + In this example, the first hunk contains just the first two lines of +`lao', the second hunk contains the fourth line of `lao' opposing the +second and third lines of `tzu', and the last hunk contains just the +last three lines of `tzu'. + + +File: diff.info, Node: Normal, Next: Context, Prev: Sample diff Input, Up: Output Formats + +Showing Differences Without Context +=================================== + + The "normal" `diff' output format shows each hunk of differences +without any surrounding context. Sometimes such output is the clearest +way to see how lines have changed, without the clutter of nearby +unchanged lines (although you can get similar results with the context +or unified formats by using 0 lines of context). However, this format +is no longer widely used for sending out patches; for that purpose, the +context format (*note Context Format::) and the unified format (*note +Unified Format::) are superior. Normal format is the default for +compatibility with older versions of `diff' and the POSIX standard. +Use the `--normal' option to select this output format explicitly. + +* Menu: + +* Detailed Normal:: A detailed description of normal output format. +* Example Normal:: Sample output in the normal format. + + +File: diff.info, Node: Detailed Normal, Next: Example Normal, Up: Normal + +Detailed Description of Normal Format +------------------------------------- + + The normal output format consists of one or more hunks of +differences; each hunk shows one area where the files differ. Normal +format hunks look like this: + + CHANGE-COMMAND + < FROM-FILE-LINE + < FROM-FILE-LINE... + --- + > TO-FILE-LINE + > TO-FILE-LINE... + + There are three types of change commands. Each consists of a line +number or comma-separated range of lines in the first file, a single +character indicating the kind of change to make, and a line number or +comma-separated range of lines in the second file. All line numbers are +the original line numbers in each file. The types of change commands +are: + +`LaR' + Add the lines in range R of the second file after line L of the + first file. For example, `8a12,15' means append lines 12-15 of + file 2 after line 8 of file 1; or, if changing file 2 into file 1, + delete lines 12-15 of file 2. + +`FcT' + Replace the lines in range F of the first file with lines in range + T of the second file. This is like a combined add and delete, but + more compact. For example, `5,7c8,10' means change lines 5-7 of + file 1 to read as lines 8-10 of file 2; or, if changing file 2 into + file 1, change lines 8-10 of file 2 to read as lines 5-7 of file 1. + +`RdL' + Delete the lines in range R from the first file; line L is where + they would have appeared in the second file had they not been + deleted. For example, `5,7d3' means delete lines 5-7 of file 1; + or, if changing file 2 into file 1, append lines 5-7 of file 1 + after line 3 of file 2. + + +File: diff.info, Node: Example Normal, Prev: Detailed Normal, Up: Normal + +An Example of Normal Format +--------------------------- + + Here is the output of the command `diff lao tzu' (*note Sample diff +Input::, for the complete contents of the two files). Notice that it +shows only the lines that are different between the two files. + + 1,2d0 + < The Way that can be told of is not the eternal Way; + < The name that can be named is not the eternal name. + 4c2,3 + < The Named is the mother of all things. + --- + > The named is the mother of all things. + > + 11a11,13 + > They both may be called deep and profound. + > Deeper and more profound, + > The door of all subtleties! + + +File: diff.info, Node: Context, Next: Side by Side, Prev: Normal, Up: Output Formats + +Showing Differences in Their Context +==================================== + + Usually, when you are looking at the differences between files, you +will also want to see the parts of the files near the lines that +differ, to help you understand exactly what has changed. These nearby +parts of the files are called the "context". + + GNU `diff' provides two output formats that show context around the +differing lines: "context format" and "unified format". It can +optionally show in which function or section of the file the differing +lines are found. + + If you are distributing new versions of files to other people in the +form of `diff' output, you should use one of the output formats that +show context so that they can apply the diffs even if they have made +small changes of their own to the files. `patch' can apply the diffs +in this case by searching in the files for the lines of context around +the differing lines; if those lines are actually a few lines away from +where the diff says they are, `patch' can adjust the line numbers +accordingly and still apply the diff correctly. *Note Imperfect::, for +more information on using `patch' to apply imperfect diffs. + +* Menu: + +* Context Format:: An output format that shows surrounding lines. +* Unified Format:: A more compact output format that shows context. +* Sections:: Showing which sections of the files differences are in. +* Alternate Names:: Showing alternate file names in context headers. + + +File: diff.info, Node: Context Format, Next: Unified Format, Up: Context + +Context Format +-------------- + + The context output format shows several lines of context around the +lines that differ. It is the standard format for distributing updates +to source code. + + To select this output format, use the `-C LINES', +`--context[=LINES]', or `-c' option. The argument LINES that some of +these options take is the number of lines of context to show. If you +do not specify LINES, it defaults to three. For proper operation, +`patch' typically needs at least two lines of context. + +* Menu: + +* Detailed Context:: A detailed description of the context output format. +* Example Context:: Sample output in context format. +* Less Context:: Another sample with less context. + + +File: diff.info, Node: Detailed Context, Next: Example Context, Up: Context Format + +Detailed Description of Context Format +...................................... + + The context output format starts with a two-line header, which looks +like this: + + *** FROM-FILE FROM-FILE-MODIFICATION-TIME + --- TO-FILE TO-FILE-MODIFICATION TIME + +The time stamp normally looks like `2002-02-21 23:30:39.942229878 +-0800' to indicate the date, time with fractional seconds, and time +zone in Internet RFC 2822 format +(ftp://ftp.isi.edu/in-notes/rfc2822.txt). However, a traditional time +stamp like `Thu Feb 21 23:30:39 2002' is used if the `LC_TIME' locale +category is either `C' or `POSIX'. + + You can change the header's content with the `--label=LABEL' option; +see *Note Alternate Names::. + + Next come one or more hunks of differences; each hunk shows one area +where the files differ. Context format hunks look like this: + + *************** + *** FROM-FILE-LINE-RANGE **** + FROM-FILE-LINE + FROM-FILE-LINE... + --- TO-FILE-LINE-RANGE ---- + TO-FILE-LINE + TO-FILE-LINE... + + The lines of context around the lines that differ start with two +space characters. The lines that differ between the two files start +with one of the following indicator characters, followed by a space +character: + +`!' + A line that is part of a group of one or more lines that changed + between the two files. There is a corresponding group of lines + marked with `!' in the part of this hunk for the other file. + +`+' + An "inserted" line in the second file that corresponds to nothing + in the first file. + +`-' + A "deleted" line in the first file that corresponds to nothing in + the second file. + + If all of the changes in a hunk are insertions, the lines of +FROM-FILE are omitted. If all of the changes are deletions, the lines +of TO-FILE are omitted. + + +File: diff.info, Node: Example Context, Next: Less Context, Prev: Detailed Context, Up: Context Format + +An Example of Context Format +............................ + + Here is the output of `diff -c lao tzu' (*note Sample diff Input::, +for the complete contents of the two files). Notice that up to three +lines that are not different are shown around each line that is +different; they are the context lines. Also notice that the first two +hunks have run together, because their contents overlap. + + *** lao 2002-02-21 23:30:39.942229878 -0800 + --- tzu 2002-02-21 23:30:50.442260588 -0800 + *************** + *** 1,7 **** + - The Way that can be told of is not the eternal Way; + - The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; + ! The Named is the mother of all things. + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + --- 1,6 ---- + The Nameless is the origin of Heaven and Earth; + ! The named is the mother of all things. + ! + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + *************** + *** 9,11 **** + --- 8,13 ---- + The two are the same, + But after they are produced, + they have different names. + + They both may be called deep and profound. + + Deeper and more profound, + + The door of all subtleties! + + +File: diff.info, Node: Less Context, Prev: Example Context, Up: Context Format + +An Example of Context Format with Less Context +.............................................. + + Here is the output of `diff -C 1 lao tzu' (*note Sample diff +Input::, for the complete contents of the two files). Notice that at +most one context line is reported here. + + *** lao 2002-02-21 23:30:39.942229878 -0800 + --- tzu 2002-02-21 23:30:50.442260588 -0800 + *************** + *** 1,5 **** + - The Way that can be told of is not the eternal Way; + - The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; + ! The Named is the mother of all things. + Therefore let there always be non-being, + --- 1,4 ---- + The Nameless is the origin of Heaven and Earth; + ! The named is the mother of all things. + ! + Therefore let there always be non-being, + *************** + *** 11 **** + --- 10,13 ---- + they have different names. + + They both may be called deep and profound. + + Deeper and more profound, + + The door of all subtleties! + + +File: diff.info, Node: Unified Format, Next: Sections, Prev: Context Format, Up: Context + +Unified Format +-------------- + + The unified output format is a variation on the context format that +is more compact because it omits redundant context lines. To select +this output format, use the `-U LINES', `--unified[=LINES]', or `-u' +option. The argument LINES is the number of lines of context to show. +When it is not given, it defaults to three. + + At present, only GNU `diff' can produce this format and only GNU +`patch' can automatically apply diffs in this format. For proper +operation, `patch' typically needs at least three lines of context. + +* Menu: + +* Detailed Unified:: A detailed description of unified format. +* Example Unified:: Sample output in unified format. + + +File: diff.info, Node: Detailed Unified, Next: Example Unified, Up: Unified Format + +Detailed Description of Unified Format +...................................... + + The unified output format starts with a two-line header, which looks +like this: + + --- FROM-FILE FROM-FILE-MODIFICATION-TIME + +++ TO-FILE TO-FILE-MODIFICATION-TIME + +The time stamp looks like `2002-02-21 23:30:39.942229878 -0800' to +indicate the date, time with fractional seconds, and time zone. + + You can change the header's content with the `--label=LABEL' option; +see *Note Alternate Names::. + + Next come one or more hunks of differences; each hunk shows one area +where the files differ. Unified format hunks look like this: + + @@ FROM-FILE-RANGE TO-FILE-RANGE @@ + LINE-FROM-EITHER-FILE + LINE-FROM-EITHER-FILE... + + The lines common to both files begin with a space character. The +lines that actually differ between the two files have one of the +following indicator characters in the left print column: + +`+' + A line was added here to the first file. + +`-' + A line was removed here from the first file. + + +File: diff.info, Node: Example Unified, Prev: Detailed Unified, Up: Unified Format + +An Example of Unified Format +............................ + + Here is the output of the command `diff -u lao tzu' (*note Sample +diff Input::, for the complete contents of the two files): + + --- lao 2002-02-21 23:30:39.942229878 -0800 + +++ tzu 2002-02-21 23:30:50.442260588 -0800 + @@ -1,7 +1,6 @@ + -The Way that can be told of is not the eternal Way; + -The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; + -The Named is the mother of all things. + +The named is the mother of all things. + + + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + @@ -9,3 +8,6 @@ + The two are the same, + But after they are produced, + they have different names. + +They both may be called deep and profound. + +Deeper and more profound, + +The door of all subtleties! + + +File: diff.info, Node: Sections, Next: Alternate Names, Prev: Unified Format, Up: Context + +Showing Which Sections Differences Are in +----------------------------------------- + + Sometimes you might want to know which part of the files each change +falls in. If the files are source code, this could mean which function +was changed. If the files are documents, it could mean which chapter or +appendix was changed. GNU `diff' can show this by displaying the +nearest section heading line that precedes the differing lines. Which +lines are "section headings" is determined by a regular expression. + +* Menu: + +* Specified Headings:: Showing headings that match regular expressions. +* C Function Headings:: Showing headings of C functions. + + +File: diff.info, Node: Specified Headings, Next: C Function Headings, Up: Sections + +Showing Lines That Match Regular Expressions +............................................ + + To show in which sections differences occur for files that are not +source code for C or similar languages, use the `-F REGEXP' or +`--show-function-line=REGEXP' option. `diff' considers lines that +match the `grep'-style regular expression REGEXP to be the beginning of +a section of the file. Here are suggested regular expressions for some +common languages: + +`^[[:alpha:]$_]' + C, C++, Prolog + +`^(' + Lisp + +`^@node' + Texinfo + + This option does not automatically select an output format; in order +to use it, you must select the context format (*note Context Format::) +or unified format (*note Unified Format::). In other output formats it +has no effect. + + The `-F' and `--show-function-line' options find the nearest +unchanged line that precedes each hunk of differences and matches the +given regular expression. Then they add that line to the end of the +line of asterisks in the context format, or to the `@@' line in unified +format. If no matching line exists, they leave the output for that +hunk unchanged. If that line is more than 40 characters long, they +output only the first 40 characters. You can specify more than one +regular expression for such lines; `diff' tries to match each line +against each regular expression, starting with the last one given. This +means that you can use `-p' and `-F' together, if you wish. + + +File: diff.info, Node: C Function Headings, Prev: Specified Headings, Up: Sections + +Showing C Function Headings +........................... + + To show in which functions differences occur for C and similar +languages, you can use the `-p' or `--show-c-function' option. This +option automatically defaults to the context output format (*note +Context Format::), with the default number of lines of context. You +can override that number with `-C LINES' elsewhere in the command line. +You can override both the format and the number with `-U LINES' +elsewhere in the command line. + + The `-p' and `--show-c-function' options are equivalent to `-F +'^[[:alpha:]$_]'' if the unified format is specified, otherwise `-c -F +'^[[:alpha:]$_]'' (*note Specified Headings::). GNU `diff' provides +them for the sake of convenience. + + +File: diff.info, Node: Alternate Names, Prev: Sections, Up: Context + +Showing Alternate File Names +---------------------------- + + If you are comparing two files that have meaningless or uninformative +names, you might want `diff' to show alternate names in the header of +the context and unified output formats. To do this, use the +`--label=LABEL' option. The first time you give this option, its +argument replaces the name and date of the first file in the header; +the second time, its argument replaces the name and date of the second +file. If you give this option more than twice, `diff' reports an +error. The `--label' option does not affect the file names in the `pr' +header when the `-l' or `--paginate' option is used (*note +Pagination::). + + Here are the first two lines of the output from `diff -C 2 +--label=original --label=modified lao tzu': + + *** original + --- modified + + +File: diff.info, Node: Side by Side, Next: Scripts, Prev: Context, Up: Output Formats + +Showing Differences Side by Side +================================ + + `diff' can produce a side by side difference listing of two files. +The files are listed in two columns with a gutter between them. The +gutter contains one of the following markers: + +white space + The corresponding lines are in common. That is, either the lines + are identical, or the difference is ignored because of one of the + `--ignore' options (*note White Space::). + +`|' + The corresponding lines differ, and they are either both complete + or both incomplete. + +`<' + The files differ and only the first file contains the line. + +`>' + The files differ and only the second file contains the line. + +`(' + Only the first file contains the line, but the difference is + ignored. + +`)' + Only the second file contains the line, but the difference is + ignored. + +`\' + The corresponding lines differ, and only the first line is + incomplete. + +`/' + The corresponding lines differ, and only the second line is + incomplete. + + Normally, an output line is incomplete if and only if the lines that +it contains are incomplete; *Note Incomplete Lines::. However, when an +output line represents two differing lines, one might be incomplete +while the other is not. In this case, the output line is complete, but +its the gutter is marked `\' if the first line is incomplete, `/' if +the second line is. + + Side by side format is sometimes easiest to read, but it has +limitations. It generates much wider output than usual, and truncates +lines that are too long to fit. Also, it relies on lining up output +more heavily than usual, so its output looks particularly bad if you +use varying width fonts, nonstandard tab stops, or nonprinting +characters. + + You can use the `sdiff' command to interactively merge side by side +differences. *Note Interactive Merging::, for more information on +merging files. + +* Menu: + +* Side by Side Format:: Controlling side by side output format. +* Example Side by Side:: Sample side by side output. + + +File: diff.info, Node: Side by Side Format, Next: Example Side by Side, Up: Side by Side + +Controlling Side by Side Format +------------------------------- + + The `-y' or `--side-by-side' option selects side by side format. +Because side by side output lines contain two input lines, the output +is wider than usual: normally 130 print columns, which can fit onto a +traditional printer line. You can set the width of the output with the +`-W COLUMNS' or `--width=COLUMNS' option. The output is split into two +halves of equal width, separated by a small gutter to mark differences; +the right half is aligned to a tab stop so that tabs line up. Input +lines that are too long to fit in half of an output line are truncated +for output. + + The `--left-column' option prints only the left column of two common +lines. The `--suppress-common-lines' option suppresses common lines +entirely. + + +File: diff.info, Node: Example Side by Side, Prev: Side by Side Format, Up: Side by Side + +An Example of Side by Side Format +--------------------------------- + + Here is the output of the command `diff -y -W 72 lao tzu' (*note +Sample diff Input::, for the complete contents of the two files). + + The Way that can be told of is n < + The name that can be named is no < + The Nameless is the origin of He The Nameless is the origin of He + The Named is the mother of all t | The named is the mother of all t + > + Therefore let there always be no Therefore let there always be no + so we may see their subtlety, so we may see their subtlety, + And let there always be being, And let there always be being, + so we may see their outcome. so we may see their outcome. + The two are the same, The two are the same, + But after they are produced, But after they are produced, + they have different names. they have different names. + > They both may be called deep and + > Deeper and more profound, + > The door of all subtleties! + + +File: diff.info, Node: Scripts, Next: If-then-else, Prev: Side by Side, Up: Output Formats + +Making Edit Scripts +=================== + + Several output modes produce command scripts for editing FROM-FILE +to produce TO-FILE. + +* Menu: + +* ed Scripts:: Using `diff' to produce commands for `ed'. +* Forward ed:: Making forward `ed' scripts. +* RCS:: A special `diff' output format used by RCS. + + +File: diff.info, Node: ed Scripts, Next: Forward ed, Up: Scripts + +`ed' Scripts +------------ + + `diff' can produce commands that direct the `ed' text editor to +change the first file into the second file. Long ago, this was the +only output mode that was suitable for editing one file into another +automatically; today, with `patch', it is almost obsolete. Use the +`-e' or `--ed' option to select this output format. + + Like the normal format (*note Normal::), this output format does not +show any context; unlike the normal format, it does not include the +information necessary to apply the diff in reverse (to produce the first +file if all you have is the second file and the diff). + + If the file `d' contains the output of `diff -e old new', then the +command `(cat d && echo w) | ed - old' edits `old' to make it a copy of +`new'. More generally, if `d1', `d2', ..., `dN' contain the outputs of +`diff -e old new1', `diff -e new1 new2', ..., `diff -e newN-1 newN', +respectively, then the command `(cat d1 d2 ... dN && echo w) | ed - +old' edits `old' to make it a copy of `newN'. + +* Menu: + +* Detailed ed:: A detailed description of `ed' format. +* Example ed:: A sample `ed' script. + + +File: diff.info, Node: Detailed ed, Next: Example ed, Up: ed Scripts + +Detailed Description of `ed' Format +................................... + + The `ed' output format consists of one or more hunks of differences. +The changes closest to the ends of the files come first so that +commands that change the number of lines do not affect how `ed' +interprets line numbers in succeeding commands. `ed' format hunks look +like this: + + CHANGE-COMMAND + TO-FILE-LINE + TO-FILE-LINE... + . + + Because `ed' uses a single period on a line to indicate the end of +input, GNU `diff' protects lines of changes that contain a single +period on a line by writing two periods instead, then writing a +subsequent `ed' command to change the two periods into one. The `ed' +format cannot represent an incomplete line, so if the second file ends +in a changed incomplete line, `diff' reports an error and then pretends +that a newline was appended. + + There are three types of change commands. Each consists of a line +number or comma-separated range of lines in the first file and a single +character indicating the kind of change to make. All line numbers are +the original line numbers in the file. The types of change commands +are: + +`La' + Add text from the second file after line L in the first file. For + example, `8a' means to add the following lines after line 8 of file + 1. + +`Rc' + Replace the lines in range R in the first file with the following + lines. Like a combined add and delete, but more compact. For + example, `5,7c' means change lines 5-7 of file 1 to read as the + text file 2. + +`Rd' + Delete the lines in range R from the first file. For example, + `5,7d' means delete lines 5-7 of file 1. + + +File: diff.info, Node: Example ed, Prev: Detailed ed, Up: ed Scripts + +Example `ed' Script +................... + + Here is the output of `diff -e lao tzu' (*note Sample diff Input::, +for the complete contents of the two files): + + 11a + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! + . + 4c + The named is the mother of all things. + + . + 1,2d + + +File: diff.info, Node: Forward ed, Next: RCS, Prev: ed Scripts, Up: Scripts + +Forward `ed' Scripts +-------------------- + + `diff' can produce output that is like an `ed' script, but with +hunks in forward (front to back) order. The format of the commands is +also changed slightly: command characters precede the lines they +modify, spaces separate line numbers in ranges, and no attempt is made +to disambiguate hunk lines consisting of a single period. Like `ed' +format, forward `ed' format cannot represent incomplete lines. + + Forward `ed' format is not very useful, because neither `ed' nor +`patch' can apply diffs in this format. It exists mainly for +compatibility with older versions of `diff'. Use the `-f' or +`--forward-ed' option to select it. + + +File: diff.info, Node: RCS, Prev: Forward ed, Up: Scripts + +RCS Scripts +----------- + + The RCS output format is designed specifically for use by the +Revision Control System, which is a set of free programs used for +organizing different versions and systems of files. Use the `-n' or +`--rcs' option to select this output format. It is like the forward +`ed' format (*note Forward ed::), but it can represent arbitrary +changes to the contents of a file because it avoids the forward `ed' +format's problems with lines consisting of a single period and with +incomplete lines. Instead of ending text sections with a line +consisting of a single period, each command specifies the number of +lines it affects; a combination of the `a' and `d' commands are used +instead of `c'. Also, if the second file ends in a changed incomplete +line, then the output also ends in an incomplete line. + + Here is the output of `diff -n lao tzu' (*note Sample diff Input::, +for the complete contents of the two files): + + d1 2 + d4 1 + a4 2 + The named is the mother of all things. + + a11 3 + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! + + +File: diff.info, Node: If-then-else, Prev: Scripts, Up: Output Formats + +Merging Files with If-then-else +=============================== + + You can use `diff' to merge two files of C source code. The output +of `diff' in this format contains all the lines of both files. Lines +common to both files are output just once; the differing parts are +separated by the C preprocessor directives `#ifdef NAME' or `#ifndef +NAME', `#else', and `#endif'. When compiling the output, you select +which version to use by either defining or leaving undefined the macro +NAME. + + To merge two files, use `diff' with the `-D NAME' or `--ifdef=NAME' +option. The argument NAME is the C preprocessor identifier to use in +the `#ifdef' and `#ifndef' directives. + + For example, if you change an instance of `wait (&s)' to `waitpid +(-1, &s, 0)' and then merge the old and new files with the +`--ifdef=HAVE_WAITPID' option, then the affected part of your code +might look like this: + + do { + #ifndef HAVE_WAITPID + if ((w = wait (&s)) < 0 && errno != EINTR) + #else /* HAVE_WAITPID */ + if ((w = waitpid (-1, &s, 0)) < 0 && errno != EINTR) + #endif /* HAVE_WAITPID */ + return w; + } while (w != child); + + You can specify formats for languages other than C by using line +group formats and line formats, as described in the next sections. + +* Menu: + +* Line Group Formats:: Formats for general if-then-else line groups. +* Line Formats:: Formats for each line in a line group. +* Detailed If-then-else:: A detailed description of if-then-else format. +* Example If-then-else:: Sample if-then-else format output. + + +File: diff.info, Node: Line Group Formats, Next: Line Formats, Up: If-then-else + +Line Group Formats +------------------ + + Line group formats let you specify formats suitable for many +applications that allow if-then-else input, including programming +languages and text formatting languages. A line group format specifies +the output format for a contiguous group of similar lines. + + For example, the following command compares the TeX files `old' and +`new', and outputs a merged file in which old regions are surrounded by +`\begin{em}'-`\end{em}' lines, and new regions are surrounded by +`\begin{bf}'-`\end{bf}' lines. + + diff \ + --old-group-format='\begin{em} + %<\end{em} + ' \ + --new-group-format='\begin{bf} + %>\end{bf} + ' \ + old new + + The following command is equivalent to the above example, but it is a +little more verbose, because it spells out the default line group +formats. + + diff \ + --old-group-format='\begin{em} + %<\end{em} + ' \ + --new-group-format='\begin{bf} + %>\end{bf} + ' \ + --unchanged-group-format='%=' \ + --changed-group-format='\begin{em} + %<\end{em} + \begin{bf} + %>\end{bf} + ' \ + old new + + Here is a more advanced example, which outputs a diff listing with +headers containing line numbers in a "plain English" style. + + diff \ + --unchanged-group-format='' \ + --old-group-format='-------- %dn line%(n=1?:s) deleted at %df: + %<' \ + --new-group-format='-------- %dN line%(N=1?:s) added after %de: + %>' \ + --changed-group-format='-------- %dn line%(n=1?:s) changed at %df: + %<-------- to: + %>' \ + old new + + To specify a line group format, use `diff' with one of the options +listed below. You can specify up to four line group formats, one for +each kind of line group. You should quote FORMAT, because it typically +contains shell metacharacters. + +`--old-group-format=FORMAT' + These line groups are hunks containing only lines from the first + file. The default old group format is the same as the changed + group format if it is specified; otherwise it is a format that + outputs the line group as-is. + +`--new-group-format=FORMAT' + These line groups are hunks containing only lines from the second + file. The default new group format is same as the changed group + format if it is specified; otherwise it is a format that outputs + the line group as-is. + +`--changed-group-format=FORMAT' + These line groups are hunks containing lines from both files. The + default changed group format is the concatenation of the old and + new group formats. + +`--unchanged-group-format=FORMAT' + These line groups contain lines common to both files. The default + unchanged group format is a format that outputs the line group + as-is. + + In a line group format, ordinary characters represent themselves; +conversion specifications start with `%' and have one of the following +forms. + +`%<' + stands for the lines from the first file, including the trailing + newline. Each line is formatted according to the old line format + (*note Line Formats::). + +`%>' + stands for the lines from the second file, including the trailing + newline. Each line is formatted according to the new line format. + +`%=' + stands for the lines common to both files, including the trailing + newline. Each line is formatted according to the unchanged line + format. + +`%%' + stands for `%'. + +`%c'C'' + where C is a single character, stands for C. C may not be a + backslash or an apostrophe. For example, `%c':'' stands for a + colon, even inside the then-part of an if-then-else format, which + a colon would normally terminate. + +`%c'\O'' + where O is a string of 1, 2, or 3 octal digits, stands for the + character with octal code O. For example, `%c'\0'' stands for a + null character. + +`FN' + where F is a `printf' conversion specification and N is one of the + following letters, stands for N's value formatted with F. + + `e' + The line number of the line just before the group in the old + file. + + `f' + The line number of the first line in the group in the old + file; equals E + 1. + + `l' + The line number of the last line in the group in the old file. + + `m' + The line number of the line just after the group in the old + file; equals L + 1. + + `n' + The number of lines in the group in the old file; equals L - + F + 1. + + `E, F, L, M, N' + Likewise, for lines in the new file. + + The `printf' conversion specification can be `%d', `%o', `%x', or + `%X', specifying decimal, octal, lower case hexadecimal, or upper + case hexadecimal output respectively. After the `%' the following + options can appear in sequence: a series of zero or more flags; an + integer specifying the minimum field width; and a period followed + by an optional integer specifying the minimum number of digits. + The flags are `-' for left-justification, `'' for separating the + digit into groups as specified by the `LC_NUMERIC' locale category, + and `0' for padding with zeros instead of spaces. For example, + `%5dN' prints the number of new lines in the group in a field of + width 5 characters, using the `printf' format `"%5d"'. + +`(A=B?T:E)' + If A equals B then T else E. A and B are each either a decimal + constant or a single letter interpreted as above. This format + spec is equivalent to T if A's value equals B's; otherwise it is + equivalent to E. + + For example, `%(N=0?no:%dN) line%(N=1?:s)' is equivalent to `no + lines' if N (the number of lines in the group in the the new file) + is 0, to `1 line' if N is 1, and to `%dN lines' otherwise. + + +File: diff.info, Node: Line Formats, Next: Detailed If-then-else, Prev: Line Group Formats, Up: If-then-else + +Line Formats +------------ + + Line formats control how each line taken from an input file is +output as part of a line group in if-then-else format. + + For example, the following command outputs text with a one-character +change indicator to the left of the text. The first character of output +is `-' for deleted lines, `|' for added lines, and a space for +unchanged lines. The formats contain newline characters where newlines +are desired on output. + + diff \ + --old-line-format='-%l + ' \ + --new-line-format='|%l + ' \ + --unchanged-line-format=' %l + ' \ + old new + + To specify a line format, use one of the following options. You +should quote FORMAT, since it often contains shell metacharacters. + +`--old-line-format=FORMAT' + formats lines just from the first file. + +`--new-line-format=FORMAT' + formats lines just from the second file. + +`--unchanged-line-format=FORMAT' + formats lines common to both files. + +`--line-format=FORMAT' + formats all lines; in effect, it sets all three above options + simultaneously. + + In a line format, ordinary characters represent themselves; +conversion specifications start with `%' and have one of the following +forms. + +`%l' + stands for the contents of the line, not counting its trailing + newline (if any). This format ignores whether the line is + incomplete; *Note Incomplete Lines::. + +`%L' + stands for the contents of the line, including its trailing newline + (if any). If a line is incomplete, this format preserves its + incompleteness. + +`%%' + stands for `%'. + +`%c'C'' + where C is a single character, stands for C. C may not be a + backslash or an apostrophe. For example, `%c':'' stands for a + colon. + +`%c'\O'' + where O is a string of 1, 2, or 3 octal digits, stands for the + character with octal code O. For example, `%c'\0'' stands for a + null character. + +`Fn' + where F is a `printf' conversion specification, stands for the + line number formatted with F. For example, `%.5dn' prints the + line number using the `printf' format `"%.5d"'. *Note Line Group + Formats::, for more about printf conversion specifications. + + The default line format is `%l' followed by a newline character. + + If the input contains tab characters and it is important that they +line up on output, you should ensure that `%l' or `%L' in a line format +is just after a tab stop (e.g. by preceding `%l' or `%L' with a tab +character), or you should use the `-t' or `--expand-tabs' option. + + Taken together, the line and line group formats let you specify many +different formats. For example, the following command uses a format +similar to normal `diff' format. You can tailor this command to get +fine control over `diff' output. + + diff \ + --old-line-format='< %l + ' \ + --new-line-format='> %l + ' \ + --old-group-format='%df%(f=l?:,%dl)d%dE + %<' \ + --new-group-format='%dea%dF%(F=L?:,%dL) + %>' \ + --changed-group-format='%df%(f=l?:,%dl)c%dF%(F=L?:,%dL) + %<--- + %>' \ + --unchanged-group-format='' \ + old new + + +File: diff.info, Node: Detailed If-then-else, Next: Example If-then-else, Prev: Line Formats, Up: If-then-else + +Detailed Description of If-then-else Format +------------------------------------------- + + For lines common to both files, `diff' uses the unchanged line group +format. For each hunk of differences in the merged output format, if +the hunk contains only lines from the first file, `diff' uses the old +line group format; if the hunk contains only lines from the second +file, `diff' uses the new group format; otherwise, `diff' uses the +changed group format. + + The old, new, and unchanged line formats specify the output format of +lines from the first file, lines from the second file, and lines common +to both files, respectively. + + The option `--ifdef=NAME' is equivalent to the following sequence of +options using shell syntax: + + --old-group-format='#ifndef NAME + %<#endif /* ! NAME */ + ' \ + --new-group-format='#ifdef NAME + %>#endif /* NAME */ + ' \ + --unchanged-group-format='%=' \ + --changed-group-format='#ifndef NAME + %<#else /* NAME */ + %>#endif /* NAME */ + ' + + You should carefully check the `diff' output for proper nesting. +For example, when using the `-D NAME' or `--ifdef=NAME' option, you +should check that if the differing lines contain any of the C +preprocessor directives `#ifdef', `#ifndef', `#else', `#elif', or +`#endif', they are nested properly and match. If they don't, you must +make corrections manually. It is a good idea to carefully check the +resulting code anyway to make sure that it really does what you want it +to; depending on how the input files were produced, the output might +contain duplicate or otherwise incorrect code. + + The `patch' `-D NAME' option behaves like the `diff' `-D NAME' +option, except it operates on a file and a diff to produce a merged +file; *Note patch Options::. + + +File: diff.info, Node: Example If-then-else, Prev: Detailed If-then-else, Up: If-then-else + +An Example of If-then-else Format +--------------------------------- + + Here is the output of `diff -DTWO lao tzu' (*note Sample diff +Input::, for the complete contents of the two files): + + #ifndef TWO + The Way that can be told of is not the eternal Way; + The name that can be named is not the eternal name. + #endif /* ! TWO */ + The Nameless is the origin of Heaven and Earth; + #ifndef TWO + The Named is the mother of all things. + #else /* TWO */ + The named is the mother of all things. + + #endif /* TWO */ + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + so we may see their outcome. + The two are the same, + But after they are produced, + they have different names. + #ifdef TWO + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! + #endif /* TWO */ + + +File: diff.info, Node: Incomplete Lines, Next: Comparing Directories, Prev: Output Formats, Up: Top + +Incomplete Lines +**************** + + When an input file ends in a non-newline character, its last line is +called an "incomplete line" because its last character is not a +newline. All other lines are called "full lines" and end in a newline +character. Incomplete lines do not match full lines unless differences +in white space are ignored (*note White Space::). + + An incomplete line is normally distinguished on output from a full +line by a following line that starts with `\'. However, the RCS format +(*note RCS::) outputs the incomplete line as-is, without any trailing +newline or following line. The side by side format normally represents +incomplete lines as-is, but in some cases uses a `\' or `/' gutter +marker; *Note Side by Side::. The if-then-else line format preserves a +line's incompleteness with `%L', and discards the newline with `%l'; +*Note Line Formats::. Finally, with the `ed' and forward `ed' output +formats (*note Output Formats::) `diff' cannot represent an incomplete +line, so it pretends there was a newline and reports an error. + + For example, suppose `F' and `G' are one-byte files that contain +just `f' and `g', respectively. Then `diff F G' outputs + + 1c1 + < f + \ No newline at end of file + --- + > g + \ No newline at end of file + +(The exact message may differ in non-English locales.) `diff -n F G' +outputs the following without a trailing newline: + + d1 1 + a1 1 + g + +`diff -e F G' reports two errors and outputs the following: + + 1c + g + . + + +File: diff.info, Node: Comparing Directories, Next: Adjusting Output, Prev: Incomplete Lines, Up: Top + +Comparing Directories +********************* + + You can use `diff' to compare some or all of the files in two +directory trees. When both file name arguments to `diff' are +directories, it compares each file that is contained in both +directories, examining file names in alphabetical order as specified by +the `LC_COLLATE' locale category. Normally `diff' is silent about +pairs of files that contain no differences, but if you use the `-s' or +`--report-identical-files' option, it reports pairs of identical files. +Normally `diff' reports subdirectories common to both directories +without comparing subdirectories' files, but if you use the `-r' or +`--recursive' option, it compares every corresponding pair of files in +the directory trees, as many levels deep as they go. + + For file names that are in only one of the directories, `diff' +normally does not show the contents of the file that exists; it reports +only that the file exists in that directory and not in the other. You +can make `diff' act as though the file existed but was empty in the +other directory, so that it outputs the entire contents of the file that +actually exists. (It is output as either an insertion or a deletion, +depending on whether it is in the first or the second directory given.) +To do this, use the `-N' or `--new-file' option. + + If the older directory contains one or more large files that are not +in the newer directory, you can make the patch smaller by using the +`--unidirectional-new-file' option instead of `-N'. This option is +like `-N' except that it only inserts the contents of files that appear +in the second directory but not the first (that is, files that were +added). At the top of the patch, write instructions for the user +applying the patch to remove the files that were deleted before +applying the patch. *Note Making Patches::, for more discussion of +making patches for distribution. + + To ignore some files while comparing directories, use the `-x +PATTERN' or `--exclude=PATTERN' option. This option ignores any files +or subdirectories whose base names match the shell pattern PATTERN. +Unlike in the shell, a period at the start of the base of a file name +matches a wildcard at the start of a pattern. You should enclose +PATTERN in quotes so that the shell does not expand it. For example, +the option `-x '*.[ao]'' ignores any file whose name ends with `.a' or +`.o'. + + This option accumulates if you specify it more than once. For +example, using the options `-x 'RCS' -x '*,v'' ignores any file or +subdirectory whose base name is `RCS' or ends with `,v'. + + If you need to give this option many times, you can instead put the +patterns in a file, one pattern per line, and use the `-X FILE' or +`--exclude-from=FILE' option. + + If you have been comparing two directories and stopped partway +through, later you might want to continue where you left off. You can +do this by using the `-S FILE' or `--starting-file=FILE' option. This +compares only the file FILE and all alphabetically later files in the +topmost directory level. + + If two directories differ only in that file names are lower case in +one directory and upper case in the upper, `diff' normally reports many +differences because it compares file names in a case sensitive way. +With the `--ignore-file-name-case' option, `diff' ignores case +differences in file names, so that for example the contents of the file +`Tao' in one directory are compared to the contents of the file `TAO' +in the other. The `--no-ignore-file-name-case' option cancels the +effect of the `--ignore-file-name-case' option, reverting to the default +behavior. + + If an `-x PATTERN', `--exclude=PATTERN', `-X FILE', or +`--exclude-from=FILE' option is specified while the +`--ignore-file-name-case' option is in effect, case is ignored when +excluding file names matching the specified patterns. + + +File: diff.info, Node: Adjusting Output, Next: diff Performance, Prev: Comparing Directories, Up: Top + +Making `diff' Output Prettier +***************************** + + `diff' provides several ways to adjust the appearance of its output. +These adjustments can be applied to any output format. + +* Menu: + +* Tabs:: Preserving the alignment of tab stops. +* Pagination:: Page numbering and time-stamping `diff' output. + + +File: diff.info, Node: Tabs, Next: Pagination, Up: Adjusting Output + +Preserving Tab Stop Alignment +============================= + + The lines of text in some of the `diff' output formats are preceded +by one or two characters that indicate whether the text is inserted, +deleted, or changed. The addition of those characters can cause tabs to +move to the next tab stop, throwing off the alignment of columns in the +line. GNU `diff' provides two ways to make tab-aligned columns line up +correctly. + + The first way is to have `diff' convert all tabs into the correct +number of spaces before outputting them; select this method with the +`-t' or `--expand-tabs' option. `diff' assumes that tab stops are set +every 8 print columns. To use this form of output with `patch', you +must give `patch' the `-l' or `--ignore-white-space' option (*note +Changed White Space::, for more information). + + The other method for making tabs line up correctly is to add a tab +character instead of a space after the indicator character at the +beginning of the line. This ensures that all following tab characters +are in the same position relative to tab stops that they were in the +original files, so that the output is aligned correctly. Its +disadvantage is that it can make long lines too long to fit on one line +of the screen or the paper. It also does not work with the unified +output format, which does not have a space character after the change +type indicator character. Select this method with the `-T' or +`--initial-tab' option. + + +File: diff.info, Node: Pagination, Prev: Tabs, Up: Adjusting Output + +Paginating `diff' Output +======================== + + It can be convenient to have long output page-numbered and +time-stamped. The `-l' and `--paginate' options do this by sending the +`diff' output through the `pr' program. Here is what the page header +might look like for `diff -lc lao tzu': + + 2002-02-22 14:20 diff -lc lao tzu Page 1 + + +File: diff.info, Node: diff Performance, Next: Comparing Three Files, Prev: Adjusting Output, Up: Top + +`diff' Performance Tradeoffs +**************************** + + GNU `diff' runs quite efficiently; however, in some circumstances +you can cause it to run faster or produce a more compact set of changes. + + One way to improve `diff' performance is to use hard or symbolic +links to files instead of copies. This improves performance because +`diff' normally does not need to read two hard or symbolic links to the +same file, since their contents must be identical. For example, +suppose you copy a large directory hierarchy, make a few changes to the +copy, and then often use `diff -r' to compare the original to the copy. +If the original files are read-only, you can greatly improve +performance by creating the copy using hard or symbolic links (e.g., +with GNU `cp -lR' or `cp -sR'). Before editing a file in the copy for +the first time, you should break the link and replace it with a regular +copy. + + You can also affect the performance of GNU `diff' by giving it +options that change the way it compares files. Performance has more +than one dimension. These options improve one aspect of performance at +the cost of another, or they improve performance in some cases while +hurting it in others. + + The way that GNU `diff' determines which lines have changed always +comes up with a near-minimal set of differences. Usually it is good +enough for practical purposes. If the `diff' output is large, you +might want `diff' to use a modified algorithm that sometimes produces a +smaller set of differences. The `-d' or `--minimal' option does this; +however, it can also cause `diff' to run more slowly than usual, so it +is not the default behavior. + + When the files you are comparing are large and have small groups of +changes scattered throughout them, you can use the +`--speed-large-files' option to make a different modification to the +algorithm that `diff' uses. If the input files have a constant small +density of changes, this option speeds up the comparisons without +changing the output. If not, `diff' might produce a larger set of +differences; however, the output will still be correct. + + Normally `diff' discards the prefix and suffix that is common to +both files before it attempts to find a minimal set of differences. +This makes `diff' run faster, but occasionally it may produce +non-minimal output. The `--horizon-lines=LINES' option prevents `diff' +from discarding the last LINES lines of the prefix and the first LINES +lines of the suffix. This gives `diff' further opportunities to find a +minimal output. + + Suppose a run of changed lines includes a sequence of lines at one +end and there is an identical sequence of lines just outside the other +end. The `diff' command is free to choose which identical sequence is +included in the hunk. In this case, `diff' normally shifts the hunk's +boundaries when this merges adjacent hunks, or shifts a hunk's lines +towards the end of the file. Merging hunks can make the output look +nicer in some cases. + + +File: diff.info, Node: Comparing Three Files, Next: diff3 Merging, Prev: diff Performance, Up: Top + +Comparing Three Files +********************* + + Use the program `diff3' to compare three files and show any +differences among them. (`diff3' can also merge files; see *Note diff3 +Merging::). + + The "normal" `diff3' output format shows each hunk of differences +without surrounding context. Hunks are labeled depending on whether +they are two-way or three-way, and lines are annotated by their +location in the input files. + + *Note Invoking diff3::, for more information on how to run `diff3'. + +* Menu: + +* Sample diff3 Input:: Sample `diff3' input for examples. +* Detailed diff3 Normal:: A detailed description of normal output format. +* diff3 Hunks:: The format of normal output format. +* Example diff3 Normal:: Sample output in the normal format. + + +File: diff.info, Node: Sample diff3 Input, Next: Detailed diff3 Normal, Up: Comparing Three Files + +A Third Sample Input File +========================= + + Here is a third sample file that will be used in examples to +illustrate the output of `diff3' and how various options can change it. +The first two files are the same that we used for `diff' (*note Sample +diff Input::). This is the third sample file, called `tao': + + The Way that can be told of is not the eternal Way; + The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; + The named is the mother of all things. + + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + so we may see their result. + The two are the same, + But after they are produced, + they have different names. + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan + + +File: diff.info, Node: Detailed diff3 Normal, Next: diff3 Hunks, Prev: Sample diff3 Input, Up: Comparing Three Files + +Detailed Description of `diff3' Normal Format +============================================= + + Each hunk begins with a line marked `===='. Three-way hunks have +plain `====' lines, and two-way hunks have `1', `2', or `3' appended to +specify which of the three input files differ in that hunk. The hunks +contain copies of two or three sets of input lines each preceded by one +or two commands identifying where the lines came from. + + Normally, two spaces precede each copy of an input line to +distinguish it from the commands. But with the `-T' or `--initial-tab' +option, `diff3' uses a tab instead of two spaces; this lines up tabs +correctly. *Note Tabs::, for more information. + + Commands take the following forms: + +`FILE:La' + This hunk appears after line L of file FILE, and contains no lines + in that file. To edit this file to yield the other files, one + must append hunk lines taken from the other files. For example, + `1:11a' means that the hunk follows line 11 in the first file and + contains no lines from that file. + +`FILE:Rc' + This hunk contains the lines in the range R of file FILE. The + range R is a comma-separated pair of line numbers, or just one + number if the range is a singleton. To edit this file to yield the + other files, one must change the specified lines to be the lines + taken from the other files. For example, `2:11,13c' means that + the hunk contains lines 11 through 13 from the second file. + + If the last line in a set of input lines is incomplete (*note +Incomplete Lines::), it is distinguished on output from a full line by +a following line that starts with `\'. + + +File: diff.info, Node: diff3 Hunks, Next: Example diff3 Normal, Prev: Detailed diff3 Normal, Up: Comparing Three Files + +`diff3' Hunks +============= + + Groups of lines that differ in two or three of the input files are +called "diff3 hunks", by analogy with `diff' hunks (*note Hunks::). If +all three input files differ in a `diff3' hunk, the hunk is called a +"three-way hunk"; if just two input files differ, it is a "two-way +hunk". + + As with `diff', several solutions are possible. When comparing the +files `A', `B', and `C', `diff3' normally finds `diff3' hunks by +merging the two-way hunks output by the two commands `diff A B' and +`diff A C'. This does not necessarily minimize the size of the output, +but exceptions should be rare. + + For example, suppose `F' contains the three lines `a', `b', `f', `G' +contains the lines `g', `b', `g', and `H' contains the lines `a', `b', +`h'. `diff3 F G H' might output the following: + + ====2 + 1:1c + 3:1c + a + 2:1c + g + ==== + 1:3c + f + 2:3c + g + 3:3c + h + +because it found a two-way hunk containing `a' in the first and third +files and `g' in the second file, then the single line `b' common to +all three files, then a three-way hunk containing the last line of each +file. + + +File: diff.info, Node: Example diff3 Normal, Prev: diff3 Hunks, Up: Comparing Three Files + +An Example of `diff3' Normal Format +=================================== + + Here is the output of the command `diff3 lao tzu tao' (*note Sample +diff3 Input::, for the complete contents of the files). Notice that it +shows only the lines that are different among the three files. + + ====2 + 1:1,2c + 3:1,2c + The Way that can be told of is not the eternal Way; + The name that can be named is not the eternal name. + 2:0a + ====1 + 1:4c + The Named is the mother of all things. + 2:2,3c + 3:4,5c + The named is the mother of all things. + + ====3 + 1:8c + 2:7c + so we may see their outcome. + 3:9c + so we may see their result. + ==== + 1:11a + 2:11,13c + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! + 3:13,14c + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan + + +File: diff.info, Node: diff3 Merging, Next: Interactive Merging, Prev: Comparing Three Files, Up: Top + +Merging From a Common Ancestor +****************************** + + When two people have made changes to copies of the same file, +`diff3' can produce a merged output that contains both sets of changes +together with warnings about conflicts. + + One might imagine programs with names like `diff4' and `diff5' to +compare more than three files simultaneously, but in practice the need +rarely arises. You can use `diff3' to merge three or more sets of +changes to a file by merging two change sets at a time. + + `diff3' can incorporate changes from two modified versions into a +common preceding version. This lets you merge the sets of changes +represented by the two newer files. Specify the common ancestor version +as the second argument and the two newer versions as the first and third +arguments, like this: + + diff3 MINE OLDER YOURS + +You can remember the order of the arguments by noting that they are in +alphabetical order. + + You can think of this as subtracting OLDER from YOURS and adding the +result to MINE, or as merging into MINE the changes that would turn +OLDER into YOURS. This merging is well-defined as long as MINE and +OLDER match in the neighborhood of each such change. This fails to be +true when all three input files differ or when only OLDER differs; we +call this a "conflict". When all three input files differ, we call the +conflict an "overlap". + + `diff3' gives you several ways to handle overlaps and conflicts. +You can omit overlaps or conflicts, or select only overlaps, or mark +conflicts with special `<<<<<<<' and `>>>>>>>' lines. + + `diff3' can output the merge results as an `ed' script that that can +be applied to the first file to yield the merged output. However, it +is usually better to have `diff3' generate the merged output directly; +this bypasses some problems with `ed'. + +* Menu: + +* Which Changes:: Selecting changes to incorporate. +* Marking Conflicts:: Marking conflicts. +* Bypassing ed:: Generating merged output directly. +* Merging Incomplete Lines:: How `diff3' merges incomplete lines. +* Saving the Changed File:: Emulating System V behavior. + + +File: diff.info, Node: Which Changes, Next: Marking Conflicts, Up: diff3 Merging + +Selecting Which Changes to Incorporate +====================================== + + You can select all unmerged changes from OLDER to YOURS for merging +into MINE with the `-e' or `--ed' option. You can select only the +nonoverlapping unmerged changes with `-3' or `--easy-only', and you can +select only the overlapping changes with `-x' or `--overlap-only'. + + The `-e', `-3' and `-x' options select only "unmerged changes", i.e. +changes where MINE and YOURS differ; they ignore changes from OLDER to +YOURS where MINE and YOURS are identical, because they assume that such +changes have already been merged. If this assumption is not a safe +one, you can use the `-A' or `--show-all' option (*note Marking +Conflicts::). + + Here is the output of the command `diff3' with each of these three +options (*note Sample diff3 Input::, for the complete contents of the +files). Notice that `-e' outputs the union of the disjoint sets of +changes output by `-3' and `-x'. + + Output of `diff3 -e lao tzu tao': + 11a + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan + . + 8c + so we may see their result. + . + + Output of `diff3 -3 lao tzu tao': + 8c + so we may see their result. + . + + Output of `diff3 -x lao tzu tao': + 11a + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan + . + + +File: diff.info, Node: Marking Conflicts, Next: Bypassing ed, Prev: Which Changes, Up: diff3 Merging + +Marking Conflicts +================= + + `diff3' can mark conflicts in the merged output by bracketing them +with special marker lines. A conflict that comes from two files A and +B is marked as follows: + + <<<<<<< A + lines from A + ======= + lines from B + >>>>>>> B + + A conflict that comes from three files A, B and C is marked as +follows: + + <<<<<<< A + lines from A + ||||||| B + lines from B + ======= + lines from C + >>>>>>> C + + The `-A' or `--show-all' option acts like the `-e' option, except +that it brackets conflicts, and it outputs all changes from OLDER to +YOURS, not just the unmerged changes. Thus, given the sample input +files (*note Sample diff3 Input::), `diff3 -A lao tzu tao' puts +brackets around the conflict where only `tzu' differs: + + <<<<<<< tzu + ======= + The Way that can be told of is not the eternal Way; + The name that can be named is not the eternal name. + >>>>>>> tao + + And it outputs the three-way conflict as follows: + + <<<<<<< lao + ||||||| tzu + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! + ======= + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan + >>>>>>> tao + + The `-E' or `--show-overlap' option outputs less information than +the `-A' or `--show-all' option, because it outputs only unmerged +changes, and it never outputs the contents of the second file. Thus +the `-E' option acts like the `-e' option, except that it brackets the +first and third files from three-way overlapping changes. Similarly, +`-X' acts like `-x', except it brackets all its (necessarily +overlapping) changes. For example, for the three-way overlapping +change above, the `-E' and `-X' options output the following: + + <<<<<<< lao + ======= + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan + >>>>>>> tao + + If you are comparing files that have meaningless or uninformative +names, you can use the `-L LABEL' or `--label=LABEL' option to show +alternate names in the `<<<<<<<', `|||||||' and `>>>>>>>' brackets. +This option can be given up to three times, once for each input file. +Thus `diff3 -A -L X -L Y -L Z A B C' acts like `diff3 -A A B C', except +that the output looks like it came from files named `X', `Y' and `Z' +rather than from files named `A', `B' and `C'. + + +File: diff.info, Node: Bypassing ed, Next: Merging Incomplete Lines, Prev: Marking Conflicts, Up: diff3 Merging + +Generating the Merged Output Directly +===================================== + + With the `-m' or `--merge' option, `diff3' outputs the merged file +directly. This is more efficient than using `ed' to generate it, and +works even with non-text files that `ed' would reject. If you specify +`-m' without an `ed' script option, `-A' (`--show-all') is assumed. + + For example, the command `diff3 -m lao tzu tao' (*note Sample diff3 +Input:: for a copy of the input files) would output the following: + + <<<<<<< tzu + ======= + The Way that can be told of is not the eternal Way; + The name that can be named is not the eternal name. + >>>>>>> tao + The Nameless is the origin of Heaven and Earth; + The Named is the mother of all things. + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, + so we may see their result. + The two are the same, + But after they are produced, + they have different names. + <<<<<<< lao + ||||||| tzu + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! + ======= + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan + >>>>>>> tao + + +File: diff.info, Node: Merging Incomplete Lines, Next: Saving the Changed File, Prev: Bypassing ed, Up: diff3 Merging + +How `diff3' Merges Incomplete Lines +=================================== + + With `-m', incomplete lines (*note Incomplete Lines::) are simply +copied to the output as they are found; if the merged output ends in an +conflict and one of the input files ends in an incomplete line, +succeeding `|||||||', `=======' or `>>>>>>>' brackets appear somewhere +other than the start of a line because they are appended to the +incomplete line. + + Without `-m', if an `ed' script option is specified and an +incomplete line is found, `diff3' generates a warning and acts as if a +newline had been present. + + +File: diff.info, Node: Saving the Changed File, Prev: Merging Incomplete Lines, Up: diff3 Merging + +Saving the Changed File +======================= + + Traditional Unix `diff3' generates an `ed' script without the +trailing `w' and `q' commands that save the changes. System V `diff3' +generates these extra commands. GNU `diff3' normally behaves like +traditional Unix `diff3', but with the `-i' option it behaves like +System V `diff3' and appends the `w' and `q' commands. + + The `-i' option requires one of the `ed' script options `-AeExX3', +and is incompatible with the merged output option `-m'. + + +File: diff.info, Node: Interactive Merging, Next: Merging with patch, Prev: diff3 Merging, Up: Top + +Interactive Merging with `sdiff' +******************************** + + With `sdiff', you can merge two files interactively based on a +side-by-side `-y' format comparison (*note Side by Side::). Use `-o +FILE' or `--output=FILE' to specify where to put the merged text. +*Note Invoking sdiff::, for more details on the options to `sdiff'. + + Another way to merge files interactively is to use the Emacs Lisp +package `emerge'. *Note emerge: (emacs)emerge, for more information. + +* Menu: + +* sdiff Option Summary:: Summary of `sdiff' options. +* Merge Commands:: Merging two files interactively. + + +File: diff.info, Node: sdiff Option Summary, Next: Merge Commands, Up: Interactive Merging + +Specifying `diff' Options to `sdiff' +==================================== + + The following `sdiff' options have the same meaning as for `diff'. +*Note diff Options::, for the use of these options. + + -a -b -d -i -t -v + -B -E -I REGEXP + + --ignore-blank-lines --ignore-case + --ignore-matching-lines=REGEXP --ignore-space-change + --ignore-tab-expansion + --left-column --minimal --speed-large-files + --strip-trailing-cr --suppress-common-lines --expand-tabs + --text --version --width=COLUMNS + + For historical reasons, `sdiff' has alternate names for some +options. The `-l' option is equivalent to the `--left-column' option, +and similarly `-s' is equivalent to `--suppress-common-lines'. The +meaning of the `sdiff' `-w' and `-W' options is interchanged from that +of `diff': with `sdiff', `-w COLUMNS' is equivalent to +`--width=COLUMNS', and `-W' is equivalent to `--ignore-all-space'. +`sdiff' without the `-o' option is equivalent to `diff' with the `-y' +or `--side-by-side' option (*note Side by Side::). + + +File: diff.info, Node: Merge Commands, Prev: sdiff Option Summary, Up: Interactive Merging + +Merge Commands +============== + + Groups of common lines, with a blank gutter, are copied from the +first file to the output. After each group of differing lines, `sdiff' +prompts with `%' and pauses, waiting for one of the following commands. +Follow each command with <RET>. + +`e' + Discard both versions. Invoke a text editor on an empty temporary + file, then copy the resulting file to the output. + +`eb' + Concatenate the two versions, edit the result in a temporary file, + then copy the edited result to the output. + +`ed' + Like `eb', except precede each version with a header that shows + what file and lines the version came from. + +`el' + Edit a copy of the left version, then copy the result to the + output. + +`er' + Edit a copy of the right version, then copy the result to the + output. + +`l' + Copy the left version to the output. + +`q' + Quit. + +`r' + Copy the right version to the output. + +`s' + Silently copy common lines. + +`v' + Verbosely copy common lines. This is the default. + + The text editor invoked is specified by the `EDITOR' environment +variable if it is set. The default is system-dependent. + + +File: diff.info, Node: Merging with patch, Next: Making Patches, Prev: Interactive Merging, Up: Top + +Merging with `patch' +******************** + + `patch' takes comparison output produced by `diff' and applies the +differences to a copy of the original file, producing a patched +version. With `patch', you can distribute just the changes to a set of +files instead of distributing the entire file set; your correspondents +can apply `patch' to update their copy of the files with your changes. +`patch' automatically determines the diff format, skips any leading or +trailing headers, and uses the headers to determine which file to +patch. This lets your correspondents feed a mail message containing a +difference listing directly to `patch'. + + `patch' detects and warns about common problems like forward +patches. It saves any patches that it could not apply. It can also +maintain a `patchlevel.h' file to ensure that your correspondents apply +diffs in the proper order. + + `patch' accepts a series of diffs in its standard input, usually +separated by headers that specify which file to patch. It applies +`diff' hunks (*note Hunks::) one by one. If a hunk does not exactly +match the original file, `patch' uses heuristics to try to patch the +file as well as it can. If no approximate match can be found, `patch' +rejects the hunk and skips to the next hunk. `patch' normally replaces +each file F with its new version, putting reject hunks (if any) into +`F.rej'. + + *Note Invoking patch::, for detailed information on the options to +`patch'. + +* Menu: + +* patch Input:: Selecting the type of `patch' input. +* Revision Control:: Getting files from RCS, SCCS, etc. +* Imperfect:: Dealing with imperfect patches. +* Creating and Removing:: Creating and removing files with a patch. +* Patching Time Stamps:: Updating time stamps on patched files. +* Multiple Patches:: Handling multiple patches in a file. +* patch Directories:: Changing directory and stripping directories. +* Backups:: Whether backup files are made. +* Backup Names:: Backup file names. +* Reject Names:: Reject file names. +* patch Messages:: Messages and questions `patch' can produce. +* patch and POSIX:: Conformance to the POSIX standard. +* patch and Tradition:: GNU versus traditional `patch'. + + +File: diff.info, Node: patch Input, Next: Revision Control, Up: Merging with patch + +Selecting the `patch' Input Format +================================== + + `patch' normally determines which `diff' format the patch file uses +by examining its contents. For patch files that contain particularly +confusing leading text, you might need to use one of the following +options to force `patch' to interpret the patch file as a certain +format of diff. The output formats listed here are the only ones that +`patch' can understand. + +`-c' +`--context' + context diff. + +`-e' +`--ed' + `ed' script. + +`-n' +`--normal' + normal diff. + +`-u' +`--unified' + unified diff. + + +File: diff.info, Node: Revision Control, Next: Imperfect, Prev: patch Input, Up: Merging with patch + +Revision Control +================ + + If a nonexistent input file is under a revision control system +supported by `patch', `patch' normally asks the user whether to get (or +check out) the file from the revision control system. Patch currently +supports RCS, ClearCase and SCCS. Under RCS and SCCS, `patch' also +asks when the input file is read-only and matches the default version +in the revision control system. + + The `-g NUM' or `--get=NUM' affects access to files under supported +revision control systems. If NUM is positive, `patch' gets the file +without asking the user; if zero, `patch' neither asks the user nor +gets the file; and if negative, `patch' asks the user before getting +the file. The default value of NUM is given by the value of the +`PATCH_GET' environment variable if it is set; if not, the default +value is zero if `patch' is conforming to POSIX, negative otherwise. +*Note patch and POSIX::. + + The choice of revision control system is unaffected by the +`VERSION_CONTROL' environment variable (*note Backup Names::). + + +File: diff.info, Node: Imperfect, Next: Creating and Removing, Prev: Revision Control, Up: Merging with patch + +Applying Imperfect Patches +========================== + + `patch' tries to skip any leading text in the patch file, apply the +diff, and then skip any trailing text. Thus you can feed a mail +message directly to `patch', and it should work. If the entire diff is +indented by a constant amount of white space, `patch' automatically +ignores the indentation. If a context diff contains trailing carriage +return on each line, `patch' automatically ignores the carriage return. +If a context diff has been encapsulated by prepending `- ' to lines +beginning with `-' as per Internet RFC 934 +(ftp://ftp.isi.edu/in-notes/rfc934.txt), `patch' automatically +unencapsulates the input. + + However, certain other types of imperfect input require user +intervention or testing. + +* Menu: + +* Changed White Space:: When tabs and spaces don't match exactly. +* Reversed Patches:: Applying reversed patches correctly. +* Inexact:: Helping `patch' find close matches. +* Dry Runs:: Predicting what `patch' will do. + + +File: diff.info, Node: Changed White Space, Next: Reversed Patches, Up: Imperfect + +Applying Patches with Changed White Space +----------------------------------------- + + Sometimes mailers, editors, or other programs change spaces into +tabs, or vice versa. If this happens to a patch file or an input file, +the files might look the same, but `patch' will not be able to match +them properly. If this problem occurs, use the `-l' or +`--ignore-white-space' option, which makes `patch' compare blank +characters (i.e. spaces and tabs) loosely so that any nonempty sequence +of blanks in the patch file matches any nonempty sequence of blanks in +the input files. Non-blank characters must still match exactly. Each +line of the context must still match a line in the input file. + + +File: diff.info, Node: Reversed Patches, Next: Inexact, Prev: Changed White Space, Up: Imperfect + +Applying Reversed Patches +------------------------- + + Sometimes people run `diff' with the new file first instead of +second. This creates a diff that is "reversed". To apply such +patches, give `patch' the `-R' or `--reverse' option. `patch' then +attempts to swap each hunk around before applying it. Rejects come out +in the swapped format. + + Often `patch' can guess that the patch is reversed. If the first +hunk of a patch fails, `patch' reverses the hunk to see if it can apply +it that way. If it can, `patch' asks you if you want to have the `-R' +option set; if it can't, `patch' continues to apply the patch normally. +This method cannot detect a reversed patch if it is a normal diff and +the first command is an append (which should have been a delete) since +appends always succeed, because a null context matches anywhere. But +most patches add or change lines rather than delete them, so most +reversed normal diffs begin with a delete, which fails, and `patch' +notices. + + If you apply a patch that you have already applied, `patch' thinks +it is a reversed patch and offers to un-apply the patch. This could be +construed as a feature. If you did this inadvertently and you don't +want to un-apply the patch, just answer `n' to this offer and to the +subsequent "apply anyway" question--or type `C-c' to kill the `patch' +process. + + +File: diff.info, Node: Inexact, Next: Dry Runs, Prev: Reversed Patches, Up: Imperfect + +Helping `patch' Find Inexact Matches +------------------------------------ + + For context diffs, and to a lesser extent normal diffs, `patch' can +detect when the line numbers mentioned in the patch are incorrect, and +it attempts to find the correct place to apply each hunk of the patch. +As a first guess, it takes the line number mentioned in the hunk, plus +or minus any offset used in applying the previous hunk. If that is not +the correct place, `patch' scans both forward and backward for a set of +lines matching the context given in the hunk. + + First `patch' looks for a place where all lines of the context +match. If it cannot find such a place, and it is reading a context or +unified diff, and the maximum fuzz factor is set to 1 or more, then +`patch' makes another scan, ignoring the first and last line of +context. If that fails, and the maximum fuzz factor is set to 2 or +more, it makes another scan, ignoring the first two and last two lines +of context are ignored. It continues similarly if the maximum fuzz +factor is larger. + + The `-F LINES' or `--fuzz=LINES' option sets the maximum fuzz factor +to LINES. This option only applies to context and unified diffs; it +ignores up to LINES lines while looking for the place to install a +hunk. Note that a larger fuzz factor increases the odds of making a +faulty patch. The default fuzz factor is 2; there is no point to +setting it to more than the number of lines of context in the diff, +ordinarily 3. + + If `patch' cannot find a place to install a hunk of the patch, it +writes the hunk out to a reject file (*note Reject Names::, for +information on how reject files are named). It writes out rejected +hunks in context format no matter what form the input patch is in. If +the input is a normal or `ed' diff, many of the contexts are simply +null. The line numbers on the hunks in the reject file may be +different from those in the patch file: they show the approximate +location where `patch' thinks the failed hunks belong in the new file +rather than in the old one. + + If the `--verbose' option is given, then as it completes each hunk +`patch' tells you whether the hunk succeeded or failed, and if it +failed, on which line (in the new file) `patch' thinks the hunk should +go. If this is different from the line number specified in the diff, +it tells you the offset. A single large offset _may_ indicate that +`patch' installed a hunk in the wrong place. `patch' also tells you if +it used a fuzz factor to make the match, in which case you should also +be slightly suspicious. + + `patch' cannot tell if the line numbers are off in an `ed' script, +and can only detect wrong line numbers in a normal diff when it finds a +change or delete command. It may have the same problem with a context +diff using a fuzz factor equal to or greater than the number of lines +of context shown in the diff (typically 3). In these cases, you should +probably look at a context diff between your original and patched input +files to see if the changes make sense. Compiling without errors is a +pretty good indication that the patch worked, but not a guarantee. + + A patch against an empty file applies to a nonexistent file, and vice +versa. *Note Creating and Removing::. + + `patch' usually produces the correct results, even when it must make +many guesses. However, the results are guaranteed only when the patch +is applied to an exact copy of the file that the patch was generated +from. + + +File: diff.info, Node: Dry Runs, Prev: Inexact, Up: Imperfect + +Predicting what `patch' will do +------------------------------- + + It may not be obvious in advance what `patch' will do with a +complicated or poorly formatted patch. If you are concerned that the +input might cause `patch' to modify the wrong files, you can use the +`--dry-run' option, which causes `patch' to print the results of +applying patches without actually changing any files. You can then +inspect the diagnostics generated by the dry run to see whether `patch' +will modify the files that you expect. If the patch does not do what +you want, you can modify the patch (or the other options to `patch') +and try another dry run. Once you are satisfied with the proposed +patch you can apply it by invoking `patch' as before, but this time +without the `--dry-run' option. + + +File: diff.info, Node: Creating and Removing, Next: Patching Time Stamps, Prev: Imperfect, Up: Merging with patch + +Creating and Removing Files +=========================== + + Sometimes when comparing two directories, a file may exist in one +directory but not the other. If you give `diff' the `-N' or +`--new-file' option, or if you supply an old or new file that is named +`/dev/null' or is empty and is dated the Epoch (1970-01-01 00:00:00 +UTC), `diff' outputs a patch that adds or deletes the contents of this +file. When given such a patch, `patch' normally creates a new file or +removes the old file. However, when conforming to POSIX (*note patch +and POSIX::), `patch' does not remove the old file, but leaves it empty. +The `-E' or `--remove-empty-files' option causes `patch' to remove +output files that are empty after applying a patch, even if the patch +does not appear to be one that removed the file. + + If the patch appears to create a file that already exists, `patch' +asks for confirmation before applying the patch. + + +File: diff.info, Node: Patching Time Stamps, Next: Multiple Patches, Prev: Creating and Removing, Up: Merging with patch + +Updating Time Stamps on Patched Files +===================================== + + When `patch' updates a file, it normally sets the file's +last-modified time stamp to the current time of day. If you are using +`patch' to track a software distribution, this can cause `make' to +incorrectly conclude that a patched file is out of date. For example, +if `syntax.c' depends on `syntax.y', and `patch' updates `syntax.c' and +then `syntax.y', then `syntax.c' will normally appear to be out of date +with respect to `syntax.y' even though its contents are actually up to +date. + + The `-Z' or `--set-utc' option causes `patch' to set a patched +file's modification and access times to the time stamps given in +context diff headers. If the context diff headers do not specify a +time zone, they are assumed to use Coordinated Universal Time (UTC, +often known as GMT). + + The `-T' or `--set-time' option acts like `-Z' or `--set-utc', +except that it assumes that the context diff headers' time stamps use +local time instead of UTC. This option is not recommended, because +patches using local time cannot easily be used by people in other time +zones, and because local time stamps are ambiguous when local clocks +move backwards during daylight-saving time adjustments. If the context +diff headers specify a time zone, this option is equivalent to `-Z' or +`--set-utc'. + + `patch' normally refrains from setting a file's time stamps if the +file's original last-modified time stamp does not match the time given +in the diff header, of if the file's contents do not exactly match the +patch. However, if the `-f' or `--force' option is given, the file's +time stamps are set regardless. + + Due to the limitations of the current `diff' format, `patch' cannot +update the times of files whose contents have not changed. Also, if +you set file time stamps to values other than the current time of day, +you should also remove (e.g., with `make clean') all files that depend +on the patched files, so that later invocations of `make' do not get +confused by the patched files' times. + + +File: diff.info, Node: Multiple Patches, Next: patch Directories, Prev: Patching Time Stamps, Up: Merging with patch + +Multiple Patches in a File +========================== + + If the patch file contains more than one patch, and if you do not +specify an input file on the command line, `patch' tries to apply each +patch as if they came from separate patch files. This means that it +determines the name of the file to patch for each patch, and that it +examines the leading text before each patch for file names and +prerequisite revision level (*note Making Patches::, for more on that +topic). + + `patch' uses the following rules to intuit a file name from the +leading text before a patch. First, `patch' takes an ordered list of +candidate file names as follows: + + * If the header is that of a context diff, `patch' takes the old and + new file names in the header. A name is ignored if it does not + have enough slashes to satisfy the `-pNUM' or `--strip=NUM' + option. The name `/dev/null' is also ignored. + + * If there is an `Index:' line in the leading garbage and if either + the old and new names are both absent or if `patch' is conforming + to POSIX, `patch' takes the name in the `Index:' line. + + * For the purpose of the following rules, the candidate file names + are considered to be in the order (old, new, index), regardless of + the order that they appear in the header. + +Then `patch' selects a file name from the candidate list as follows: + + * If some of the named files exist, `patch' selects the first name + if conforming to POSIX, and the best name otherwise. + + * If `patch' is not ignoring RCS, ClearCase, and SCCS (*note + Revision Control::), and no named files exist but an RCS, + ClearCase, or SCCS master is found, `patch' selects the first + named file with an RCS, ClearCase, or SCCS master. + + * If no named files exist, no RCS, ClearCase, or SCCS master was + found, some names are given, `patch' is not conforming to POSIX, + and the patch appears to create a file, `patch' selects the best + name requiring the creation of the fewest directories. + + * If no file name results from the above heuristics, you are asked + for the name of the file to patch, and `patch' selects that name. + + To determine the "best" of a nonempty list of file names, `patch' +first takes all the names with the fewest path name components; of +those, it then takes all the names with the shortest basename; of +those, it then takes all the shortest names; finally, it takes the +first remaining name. + + *Note patch and POSIX::, to see whether `patch' is conforming to +POSIX. + + +File: diff.info, Node: patch Directories, Next: Backups, Prev: Multiple Patches, Up: Merging with patch + +Applying Patches in Other Directories +===================================== + + The `-d DIRECTORY' or `--directory=DIRECTORY' option to `patch' +makes directory DIRECTORY the current directory for interpreting both +file names in the patch file, and file names given as arguments to +other options (such as `-B' and `-o'). For example, while in a mail +reading program, you can patch a file in the `/usr/src/emacs' directory +directly from a message containing the patch like this: + + | patch -d /usr/src/emacs + + Sometimes the file names given in a patch contain leading +directories, but you keep your files in a directory different from the +one given in the patch. In those cases, you can use the `-pNUMBER' or +`--strip=NUMBER' option to set the file name strip count to NUMBER. +The strip count tells `patch' how many slashes, along with the directory +names between them, to strip from the front of file names. A sequence +of one or more adjacent slashes is counted as a single slash. By +default, `patch' strips off all leading directories, leaving just the +base file names. + + For example, suppose the file name in the patch file is +`/gnu/src/emacs/etc/NEWS'. Using `-p0' gives the entire file name +unmodified, `-p1' gives `gnu/src/emacs/etc/NEWS' (no leading slash), +`-p4' gives `etc/NEWS', and not specifying `-p' at all gives `NEWS'. + + `patch' looks for each file (after any slashes have been stripped) +in the current directory, or if you used the `-d DIRECTORY' option, in +that directory. + + +File: diff.info, Node: Backups, Next: Backup Names, Prev: patch Directories, Up: Merging with patch + +Backup Files +============ + + Normally, `patch' creates a backup file if the patch does not +exactly match the original input file, because in that case the +original data might not be recovered if you undo the patch with `patch +-R' (*note Reversed Patches::). However, when conforming to POSIX, +`patch' does not create backup files by default. *Note patch and +POSIX::. + + The `-b' or `--backup' option causes `patch' to make a backup file +regardless of whether the patch matches the original input. The +`--backup-if-mismatch' option causes `patch' to create backup files for +mismatches files; this is the default when not conforming to POSIX. The +`--no-backup-if-mismatch' option causes `patch' to not create backup +files, even for mismatched patches; this is the default when conforming +to POSIX. + + When backing up a file that does not exist, an empty, unreadable +backup file is created as a placeholder to represent the nonexistent +file. + + +File: diff.info, Node: Backup Names, Next: Reject Names, Prev: Backups, Up: Merging with patch + +Backup File Names +================= + + Normally, `patch' renames an original input file into a backup file +by appending to its name the extension `.orig', or `~' if using `.orig' +would make the backup file name too long.(1) The `-z BACKUP-SUFFIX' or +`--suffix=BACKUP-SUFFIX' option causes `patch' to use BACKUP-SUFFIX as +the backup extension instead. + + Alternately, you can specify the extension for backup files with the +`SIMPLE_BACKUP_SUFFIX' environment variable, which the options override. + + `patch' can also create numbered backup files the way GNU Emacs +does. With this method, instead of having a single backup of each file, +`patch' makes a new backup file name each time it patches a file. For +example, the backups of a file named `sink' would be called, +successively, `sink.~1~', `sink.~2~', `sink.~3~', etc. + + The `-V BACKUP-STYLE' or `--version-control=BACKUP-STYLE' option +takes as an argument a method for creating backup file names. You can +alternately control the type of backups that `patch' makes with the +`PATCH_VERSION_CONTROL' environment variable, which the `-V' option +overrides. If `PATCH_VERSION_CONTROL' is not set, the +`VERSION_CONTROL' environment variable is used instead. Please note +that these options and variables control backup file names; they do not +affect the choice of revision control system (*note Revision Control::). + + The values of these environment variables and the argument to the +`-V' option are like the GNU Emacs `version-control' variable (*note +Backup Names: (emacs)Backup Names., for more information on backup +versions in Emacs). They also recognize synonyms that are more +descriptive. The valid values are listed below; unique abbreviations +are acceptable. + +`t' +`numbered' + Always make numbered backups. + +`nil' +`existing' + Make numbered backups of files that already have them, simple + backups of the others. This is the default. + +`never' +`simple' + Always make simple backups. + + You can also tell `patch' to prepend a prefix, such as a directory +name, to produce backup file names. The `-B PREFIX' or +`--prefix=PREFIX' option makes backup files by prepending PREFIX to +them. The `-Y PREFIX' or `--basename-prefix=PREFIX' prepends PREFIX to +the last file name component of backup file names instead; for example, +`-Y ~' causes the backup name for `dir/file.c' to be `dir/~file.c'. If +you use either of these prefix options, the suffix-based options are +ignored. + + If you specify the output file with the `-o' option, that file is +the one that is backed up, not the input file. + + Options that affect the names of backup files do not affect whether +backups are made. For example, if you specify the +`--no-backup-if-mismatch' option, none of the options described in this +section have any affect, because no backups are made. + + ---------- Footnotes ---------- + + (1) A coding error in GNU `patch' version 2.5.4 causes it to always +use `~', but this should be fixed in the next release. + + +File: diff.info, Node: Reject Names, Next: patch Messages, Prev: Backup Names, Up: Merging with patch + +Reject File Names +================= + + The names for reject files (files containing patches that `patch' +could not find a place to apply) are normally the name of the output +file with `.rej' appended (or `#' if if using `.rej' would make the +backup file name too long). + + Alternatively, you can tell `patch' to place all of the rejected +patches in a single file. The `-r REJECT-FILE' or +`--reject-file=REJECT-FILE' option uses REJECT-FILE as the reject file +name. + + +File: diff.info, Node: patch Messages, Next: patch and POSIX, Prev: Reject Names, Up: Merging with patch + +Messages and Questions from `patch' +=================================== + + `patch' can produce a variety of messages, especially if it has +trouble decoding its input. In a few situations where it's not sure +how to proceed, `patch' normally prompts you for more information from +the keyboard. There are options to produce more or fewer messages, to +have it not ask for keyboard input, and to affect the way that file +names are quoted in messages. + +* Menu: + +* More or Fewer Messages:: Controlling the verbosity of `patch'. +* patch and Keyboard Input:: Inhibiting keyboard input. +* patch Quoting Style:: Quoting file names in diagnostics. + + `patch' exits with status 0 if all hunks are applied successfully, 1 +if some hunks cannot be applied, and 2 if there is more serious trouble. +When applying a set of patches in a loop, you should check the exit +status, so you don't apply a later patch to a partially patched file. + + +File: diff.info, Node: More or Fewer Messages, Next: patch and Keyboard Input, Up: patch Messages + +Controlling the Verbosity of `patch' +------------------------------------ + + You can cause `patch' to produce more messages by using the +`--verbose' option. For example, when you give this option, the +message `Hmm...' indicates that `patch' is reading text in the patch +file, attempting to determine whether there is a patch in that text, +and if so, what kind of patch it is. + + You can inhibit all terminal output from `patch', unless an error +occurs, by using the `-s', `--quiet', or `--silent' option. + + +File: diff.info, Node: patch and Keyboard Input, Next: patch Quoting Style, Prev: More or Fewer Messages, Up: patch Messages + +Inhibiting Keyboard Input +------------------------- + + There are two ways you can prevent `patch' from asking you any +questions. The `-f' or `--force' option assumes that you know what you +are doing. It causes `patch' to do the following: + + * Skip patches that do not contain file names in their headers. + + * Patch files even though they have the wrong version for the + `Prereq:' line in the patch; + + * Assume that patches are not reversed even if they look like they + are. + +The `-t' or `--batch' option is similar to `-f', in that it suppresses +questions, but it makes somewhat different assumptions: + + * Skip patches that do not contain file names in their headers (the + same as `-f'). + + * Skip patches for which the file has the wrong version for the + `Prereq:' line in the patch; + + * Assume that patches are reversed if they look like they are. + + +File: diff.info, Node: patch Quoting Style, Prev: patch and Keyboard Input, Up: patch Messages + +`patch' Quoting Style +--------------------- + + When `patch' outputs a file name in a diagnostic message, it can +format the name in any of several ways. This can be useful to output +file names unambiguously, even if they contain punctuation or special +characters like newlines. The `--quoting-style=WORD' option controls +how names are output. The WORD should be one of the following: + +`literal' + Output names as-is. + +`shell' + Quote names for the shell if they contain shell metacharacters or + would cause ambiguous output. + +`shell-always' + Quote names for the shell, even if they would normally not require + quoting. + +`c' + Quote names as for a C language string. + +`escape' + Quote as with `c' except omit the surrounding double-quote + characters. + + You can specify the default value of the `--quoting-style' option +with the environment variable `QUOTING_STYLE'. If that environment +variable is not set, the default value is `shell', but this default may +change in a future version of `patch'. + + +File: diff.info, Node: patch and POSIX, Next: patch and Tradition, Prev: patch Messages, Up: Merging with patch + +`patch' and the POSIX Standard +============================== + + If you specify the `--posix' option, or set the `POSIXLY_CORRECT' +environment variable, `patch' conforms more strictly to the POSIX +standard, as follows: + + * Take the first existing file from the list (old, new, index) when + intuiting file names from diff headers. *Note Multiple Patches::. + + * Do not remove files that are removed by a diff. *Note Creating + and Removing::. + + * Do not ask whether to get files from RCS, ClearCase, or SCCS. + *Note Revision Control::. + + * Require that all options precede the files in the command line. + + * Do not backup files, even when there is a mismatch. *Note + Backups::. + + + +File: diff.info, Node: patch and Tradition, Prev: patch and POSIX, Up: Merging with patch + +GNU `patch' and Traditional `patch' +=================================== + + The current version of GNU `patch' normally follows the POSIX +standard. *Note patch and POSIX::, for the few exceptions to this +general rule. + + Unfortunately, POSIX redefined the behavior of `patch' in several +important ways. You should be aware of the following differences if +you must interoperate with traditional `patch', or with GNU `patch' +version 2.1 and earlier. + + * In traditional `patch', the `-p' option's operand was optional, + and a bare `-p' was equivalent to `-p0'. The `-p' option now + requires an operand, and `-p 0' is now equivalent to `-p0'. For + maximum compatibility, use options like `-p0' and `-p1'. + + Also, traditional `patch' simply counted slashes when stripping + path prefixes; `patch' now counts pathname components. That is, a + sequence of one or more adjacent slashes now counts as a single + slash. For maximum portability, avoid sending patches containing + `//' in file names. + + * In traditional `patch', backups were enabled by default. This + behavior is now enabled with the `-b' or `--backup' option. + + Conversely, in POSIX `patch', backups are never made, even when + there is a mismatch. In GNU `patch', this behavior is enabled + with the `--no-backup-if-mismatch' option, or by conforming to + POSIX. + + The `-b SUFFIX' option of traditional `patch' is equivalent to the + `-b -z SUFFIX' options of GNU `patch'. + + * Traditional `patch' used a complicated (and incompletely + documented) method to intuit the name of the file to be patched + from the patch header. This method did not conform to POSIX, and + had a few gotchas. Now `patch' uses a different, equally + complicated (but better documented) method that is optionally + POSIX-conforming; we hope it has fewer gotchas. The two methods + are compatible if the file names in the context diff header and the + `Index:' line are all identical after prefix-stripping. Your + patch is normally compatible if each header's file names all + contain the same number of slashes. + + * When traditional `patch' asked the user a question, it sent the + question to standard error and looked for an answer from the first + file in the following list that was a terminal: standard error, + standard output, `/dev/tty', and standard input. Now `patch' + sends questions to standard output and gets answers from + `/dev/tty'. Defaults for some answers have been changed so that + `patch' never goes into an infinite loop when using default + answers. + + * Traditional `patch' exited with a status value that counted the + number of bad hunks, or with status 1 if there was real trouble. + Now `patch' exits with status 1 if some hunks failed, or with 2 if + there was real trouble. + + * Limit yourself to the following options when sending instructions + meant to be executed by anyone running GNU `patch', traditional + `patch', or a `patch' that conforms to POSIX. Spaces are + significant in the following list, and operands are required. + + `-c' + `-d DIR' + `-D DEFINE' + `-e' + `-l' + `-n' + `-N' + `-o OUTFILE' + `-pNUM' + `-R' + `-r REJECTFILE' + + + +File: diff.info, Node: Making Patches, Next: Invoking cmp, Prev: Merging with patch, Up: Top + +Tips for Making and Using Patches +********************************* + + Use some common sense when making and using patches. For example, +when sending bug fixes to a program's maintainer, send several small +patches, one per independent subject, instead of one large, +harder-to-digest patch that covers all the subjects. + + Here are some other things you should keep in mind if you are going +to distribute patches for updating a software package. + +* Menu: + +* Tips for Patch Producers:: Advice for making patches. +* Tips for Patch Consumers:: Advice for using patches. +* Avoiding Common Mistakes:: Avoiding common mistakes when using `patch'. +* Generating Smaller Patches:: How to generate smaller patches. + + +File: diff.info, Node: Tips for Patch Producers, Next: Tips for Patch Consumers, Up: Making Patches + +Tips for Patch Producers +======================== + + To create a patch that changes an older version of a package into a +newer version, first make a copy of the older and newer versions in +adjacent subdirectories. It is common to do that by unpacking `tar' +archives of the two versions. + + To generate the patch, use the command `diff -Naur OLD NEW' where +OLD and NEW identify the old and new directories. The names OLD and +NEW should not contain any slashes. The `-N' option lets the patch +create and remove files; `-a' lets the patch update non-text files; `-u' +generates useful time stamps and enough context; and `-r' lets the +patch update subdirectories. Here is an example command, using Bourne +shell syntax: + + diff -Naur gcc-3.0.3 gcc-3.0.4 + + Tell your recipients how to apply the patches. This should include +which working directory to use, and which `patch' options to use; the +option `-p1' is recommended. Test your procedure by pretending to be a +recipient and applying your patches to a copy of the original files. + + *Note Avoiding Common Mistakes::, for how to avoid common mistakes +when generating a patch. + + +File: diff.info, Node: Tips for Patch Consumers, Next: Avoiding Common Mistakes, Prev: Tips for Patch Producers, Up: Making Patches + +Tips for Patch Consumers +======================== + + A patch producer should tell recipients how to apply the patches, so +the first rule of thumb for a patch consumer is to follow the +instructions supplied with the patch. + + GNU `diff' can analyze files with arbitrarily long lines and files +that end in incomplete lines. However, older versions of `patch' +cannot patch such files. If you are having trouble applying such +patches, try upgrading to a recent version of GNU `patch'. + + +File: diff.info, Node: Avoiding Common Mistakes, Next: Generating Smaller Patches, Prev: Tips for Patch Consumers, Up: Making Patches + +Avoiding Common Mistakes +======================== + + When producing a patch for multiple files, apply `diff' to +directories whose names do not have slashes. This reduces confusion +when the patch consumer specifies the `-pNUMBER' option, since this +option can have surprising results when the old and new file names have +different numbers of slashes. For example, do not send a patch with a +header that looks like this: + + diff -Naur v2.0.29/prog/README prog/README + --- v2.0.29/prog/README 2002-03-10 23:30:39.942229878 -0800 + +++ prog/README 2002-03-17 20:49:32.442260588 -0800 + +because the two file names have different numbers of slashes, and +different versions of `patch' interpret the file names differently. To +avoid confusion, send output that looks like this instead: + + diff -Naur v2.0.29/prog/README v2.0.30/prog/README + --- v2.0.29/prog/README 2002-03-10 23:30:39.942229878 -0800 + +++ v2.0.30/prog/README 2002-03-17 20:49:32.442260588 -0800 + + Make sure you have specified the file names correctly, either in a +context diff header or with an `Index:' line. Take care to not send out +reversed patches, since these make people wonder whether they have +already applied the patch. + + Avoid sending patches that compare backup file names like +`README.orig' or `README~', since this might confuse `patch' into +patching a backup file instead of the real file. Instead, send patches +that compare the same base file names in different directories, e.g. +`old/README' and `new/README'. + + To save people from partially applying a patch before other patches +that should have gone before it, you can make the first patch in the +patch file update a file with a name like `patchlevel.h' or +`version.c', which contains a patch level or version number. If the +input file contains the wrong version number, `patch' will complain +immediately. + + An even clearer way to prevent this problem is to put a `Prereq:' +line before the patch. If the leading text in the patch file contains a +line that starts with `Prereq:', `patch' takes the next word from that +line (normally a version number) and checks whether the next input file +contains that word, preceded and followed by either white space or a +newline. If not, `patch' prompts you for confirmation before +proceeding. This makes it difficult to accidentally apply patches in +the wrong order. + + +File: diff.info, Node: Generating Smaller Patches, Prev: Avoiding Common Mistakes, Up: Making Patches + +Generating Smaller Patches +========================== + + The simplest way to generate a patch is to use `diff -Naur' (*note +Tips for Patch Producers::), but you might be able to reduce the size +of the patch by renaming or removing some files before making the +patch. If the older version of the package contains any files that the +newer version does not, or if any files have been renamed between the +two versions, make a list of `rm' and `mv' commands for the user to +execute in the old version directory before applying the patch. Then +run those commands yourself in the scratch directory. + + If there are any files that you don't need to include in the patch +because they can easily be rebuilt from other files (for example, +`TAGS' and output from `yacc' and `makeinfo'), exclude them from the +patch by giving `diff' the `-x PATTERN' option (*note Comparing +Directories::). If you want your patch to modify a derived file +because your recipients lack tools to build it, make sure that the +patch for the derived file follows any patches for files that it +depends on, so that the recipients' time stamps will not confuse `make'. + + Now you can create the patch using `diff -Naur'. Make sure to +specify the scratch directory first and the newer directory second. + + Add to the top of the patch a note telling the user any `rm' and +`mv' commands to run before applying the patch. Then you can remove +the scratch directory. + + You can also shrink the patch size by using fewer lines of context, +but bear in mind that `patch' typically needs at least two lines for +proper operation when patches do not exactly match the input files. + + +File: diff.info, Node: Invoking cmp, Next: Invoking diff, Prev: Making Patches, Up: Top + +Invoking `cmp' +************** + + The `cmp' command compares two files, and if they differ, tells the +first byte and line number where they differ. Bytes and lines are +numbered starting with 1. The arguments of `cmp' are as follows: + + cmp OPTIONS... FROM-FILE [TO-FILE [FROM-SKIP [TO-SKIP]]] + + The file name `-' is always the standard input. `cmp' also uses the +standard input if one file name is omitted. The FROM-SKIP and TO-SKIP +operands specify how many bytes to ignore at the start of each file; +they are equivalent to the `--ignore-initial=FROM-SKIP:TO-SKIP' option. + + An exit status of 0 means no differences were found, 1 means some +differences were found, and 2 means trouble. + +* Menu: + +* cmp Options:: Summary of options to `cmp'. + + +File: diff.info, Node: cmp Options, Up: Invoking cmp + +Options to `cmp' +================ + + Below is a summary of all of the options that GNU `cmp' accepts. +Most options have two equivalent names, one of which is a single letter +preceded by `-', and the other of which is a long name preceded by +`--'. Multiple single letter options (unless they take an argument) +can be combined into a single command line word: `-bl' is equivalent to +`-b -l'. + +`-b' +`--print-bytes' + Print the differing bytes. Display control bytes as a `^' + followed by a letter of the alphabet and precede bytes that have + the high bit set with `M-' (which stands for "meta"). + +`--help' + Output a summary of usage and then exit. + +`-i SKIP' +`--ignore-initial=SKIP' + Ignore any differences in the first SKIP bytes of the input files. + Treat files with fewer than SKIP bytes as if they are empty. If + SKIP is of the form `FROM-SKIP:TO-SKIP', skip the first FROM-SKIP + bytes of the first input file and the first TO-SKIP bytes of the + second. + +`-l' +`--verbose' + Print the (decimal) byte numbers and (octal) values of all + differing bytes. + +`-n COUNT' +`--bytes=COUNT' + Compare at most COUNT input bytes. + +`-s' +`--quiet' +`--silent' + Do not print anything; only return an exit status indicating + whether the files differ. + +`-v' +`--version' + Output version information and then exit. + + In the above table, operands that are byte counts are normally +decimal, but may be preceded by `0' for octal and `0x' for hexadecimal. + + A byte count can be followed by a suffix to specify a multiple of +that count; in this case an omitted integer is understood to be 1. A +bare size letter, or one followed by `iB', specifies a multiple using +powers of 1024. A size letter followed by `B' specifies powers of 1000 +instead. For example, `-n 4M' and `-n 4MiB' are equivalent to `-n +4194304', whereas `-n 4MB' is equivalent to `-n 4000000'. This +notation is upward compatible with the SI prefixes +(http://www.bipm.fr/enus/3_SI/si-prefixes.html) for decimal multiples +and with the IEC 60027-2 prefixes for binary multiples +(http://physics.nist.gov/cuu/Units/binary.html). + + The following suffixes are defined. Large sizes like `1Y' may be +rejected by your computer due to limitations of its arithmetic. + +`kB' + kilobyte: 10^3 = 1000. + +`k' +`K' +`KiB' + kibibyte: 2^10 = 1024. `K' is special: the SI prefix is `k' and + the IEC 60027-2 prefix is `Ki', but tradition and POSIX use `k' to + mean `KiB'. + +`MB' + megabyte: 10^6 = 1,000,000. + +`M' +`MiB' + mebibyte: 2^20 = 1,048,576. + +`GB' + gigabyte: 10^9 = 1,000,000,000. + +`G' +`GiB' + gibibyte: 2^30 = 1,073,741,824. + +`TB' + terabyte: 10^12 = 1,000,000,000,000. + +`T' +`TiB' + tebibyte: 2^40 = 1,099,511,627,776. + +`PB' + petabyte: 10^15 = 1,000,000,000,000,000. + +`P' +`PiB' + pebibyte: 2^50 = 1,125,899,906,842,624. + +`EB' + exabyte: 10^18 = 1,000,000,000,000,000,000. + +`E' +`EiB' + exbibyte: 2^60 = 1,152,921,504,606,846,976. + +`ZB' + zettabyte: 10^21 = 1,000,000,000,000,000,000,000 + +`Z' +`ZiB' + 2^70 = 1,180,591,620,717,411,303,424. (`Zi' is a GNU extension to + IEC 60027-2.) + +`YB' + yottabyte: 10^24 = 1,000,000,000,000,000,000,000,000. + +`Y' +`YiB' + 2^80 = 1,208,925,819,614,629,174,706,176. (`Yi' is a GNU + extension to IEC 60027-2.) + + +File: diff.info, Node: Invoking diff, Next: Invoking diff3, Prev: Invoking cmp, Up: Top + +Invoking `diff' +*************** + + The format for running the `diff' command is: + + diff OPTIONS... FILES... + + In the simplest case, two file names FROM-FILE and TO-FILE are +given, and `diff' compares the contents of FROM-FILE and TO-FILE. A +file name of `-' stands for text read from the standard input. As a +special case, `diff - -' compares a copy of standard input to itself. + + If one file is a directory and the other is not, `diff' compares the +file in the directory whose name is that of the non-directory. The +non-directory file must not be `-'. + + If two file names are given and both are directories, `diff' +compares corresponding files in both directories, in alphabetical +order; this comparison is not recursive unless the `-r' or +`--recursive' option is given. `diff' never compares the actual +contents of a directory as if it were a file. The file that is fully +specified may not be standard input, because standard input is nameless +and the notion of "file with the same name" does not apply. + + If the `--from-file=FILE' option is given, the number of file names +is arbitrary, and FILE is compared to each named file. Similarly, if +the `--to-file=FILE' option is given, each named file is compared to +FILE. + + `diff' options begin with `-', so normally file names may not begin +with `-'. However, `--' as an argument by itself treats the remaining +arguments as file names even if they begin with `-'. + + An exit status of 0 means no differences were found, 1 means some +differences were found, and 2 means trouble. + +* Menu: + +* diff Options:: Summary of options to `diff'. + + +File: diff.info, Node: diff Options, Up: Invoking diff + +Options to `diff' +================= + + Below is a summary of all of the options that GNU `diff' accepts. +Most options have two equivalent names, one of which is a single letter +preceded by `-', and the other of which is a long name preceded by +`--'. Multiple single letter options (unless they take an argument) +can be combined into a single command line word: `-ac' is equivalent to +`-a -c'. Long named options can be abbreviated to any unique prefix of +their name. Brackets ([ and ]) indicate that an option takes an +optional argument. + +`-a' +`--text' + Treat all files as text and compare them line-by-line, even if they + do not seem to be text. *Note Binary::. + +`-b' +`--ignore-space-change' + Ignore changes in amount of white space. *Note White Space::. + +`-B' +`--ignore-blank-lines' + Ignore changes that just insert or delete blank lines. *Note + Blank Lines::. + +`--binary' + Read and write data in binary mode. *Note Binary::. + +`-c' + Use the context output format, showing three lines of context. + *Note Context Format::. + +`-C LINES' +`--context[=LINES]' + Use the context output format, showing LINES (an integer) lines of + context, or three if LINES is not given. *Note Context Format::. + For proper operation, `patch' typically needs at least two lines of + context. + + On older systems, `diff' supports an obsolete option `-LINES' that + has effect when combined with `-c' or `-p'. POSIX 1003.1-2001 + (*note Standards conformance::) does not allow this; use `-C LINES' + instead. + +`--changed-group-format=FORMAT' + Use FORMAT to output a line group containing differing lines from + both files in if-then-else format. *Note Line Group Formats::. + +`-d' +`--minimal' + Change the algorithm perhaps find a smaller set of changes. This + makes `diff' slower (sometimes much slower). *Note diff + Performance::. + +`-D NAME' +`--ifdef=NAME' + Make merged `#ifdef' format output, conditional on the preprocessor + macro NAME. *Note If-then-else::. + +`-e' +`--ed' + Make output that is a valid `ed' script. *Note ed Scripts::. + +`-E' +`--ignore-tab-expansion' + Ignore changes due to tab expansion. *Note White Space::. + +`-f' +`--forward-ed' + Make output that looks vaguely like an `ed' script but has changes + in the order they appear in the file. *Note Forward ed::. + +`-F REGEXP' +`--show-function-line=REGEXP' + In context and unified format, for each hunk of differences, show + some of the last preceding line that matches REGEXP. *Note + Specified Headings::. + +`--from-file=FILE' + Compare FILE to each operand; FILE may be a directory. + +`--help' + Output a summary of usage and then exit. + +`--horizon-lines=LINES' + Do not discard the last LINES lines of the common prefix and the + first LINES lines of the common suffix. *Note diff Performance::. + +`-i' +`--ignore-case' + Ignore changes in case; consider upper- and lower-case letters + equivalent. *Note Case Folding::. + +`-I REGEXP' +`--ignore-matching-lines=REGEXP' + Ignore changes that just insert or delete lines that match REGEXP. + *Note Specified Folding::. + +`--ignore-file-name-case' + Ignore case when comparing file names during recursive comparison. + *Note Comparing Directories::. + +`-l' +`--paginate' + Pass the output through `pr' to paginate it. *Note Pagination::. + +`--label=LABEL' + Use LABEL instead of the file name in the context format (*note + Context Format::) and unified format (*note Unified Format::) + headers. *Note RCS::. + +`--left-column' + Print only the left column of two common lines in side by side + format. *Note Side by Side Format::. + +`--line-format=FORMAT' + Use FORMAT to output all input lines in if-then-else format. + *Note Line Formats::. + +`-n' +`--rcs' + Output RCS-format diffs; like `-f' except that each command + specifies the number of lines affected. *Note RCS::. + +`-N' +`--new-file' + In directory comparison, if a file is found in only one directory, + treat it as present but empty in the other directory. *Note + Comparing Directories::. + +`--new-group-format=FORMAT' + Use FORMAT to output a group of lines taken from just the second + file in if-then-else format. *Note Line Group Formats::. + +`--new-line-format=FORMAT' + Use FORMAT to output a line taken from just the second file in + if-then-else format. *Note Line Formats::. + +`--old-group-format=FORMAT' + Use FORMAT to output a group of lines taken from just the first + file in if-then-else format. *Note Line Group Formats::. + +`--old-line-format=FORMAT' + Use FORMAT to output a line taken from just the first file in + if-then-else format. *Note Line Formats::. + +`-p' +`--show-c-function' + Show which C function each change is in. *Note C Function + Headings::. + +`-q' +`--brief' + Report only whether the files differ, not the details of the + differences. *Note Brief::. + +`-r' +`--recursive' + When comparing directories, recursively compare any subdirectories + found. *Note Comparing Directories::. + +`-s' +`--report-identical-files' + Report when two files are the same. *Note Comparing Directories::. + +`-S FILE' +`--starting-file=FILE' + When comparing directories, start with the file FILE. This is + used for resuming an aborted comparison. *Note Comparing + Directories::. + +`--speed-large-files' + Use heuristics to speed handling of large files that have numerous + scattered small changes. *Note diff Performance::. + +`--strip-trailing-cr' + Strip any trailing carriage return at the end of an input line. + *Note Binary::. + +`--suppress-common-lines' + Do not print common lines in side by side format. *Note Side by + Side Format::. + +`-t' +`--expand-tabs' + Expand tabs to spaces in the output, to preserve the alignment of + tabs in the input files. *Note Tabs::. + +`-T' +`--initial-tab' + Output a tab rather than a space before the text of a line in + normal or context format. This causes the alignment of tabs in + the line to look normal. *Note Tabs::. + +`--to-file=FILE' + Compare each operand to FILE; FILE may be a directory. + +`-u' + Use the unified output format, showing three lines of context. + *Note Unified Format::. + +`--unchanged-group-format=FORMAT' + Use FORMAT to output a group of common lines taken from both files + in if-then-else format. *Note Line Group Formats::. + +`--unchanged-line-format=FORMAT' + Use FORMAT to output a line common to both files in if-then-else + format. *Note Line Formats::. + +`--unidirectional-new-file' + When comparing directories, if a file appears only in the second + directory of the two, treat it as present but empty in the other. + *Note Comparing Directories::. + +`-U LINES' +`--unified[=LINES]' + Use the unified output format, showing LINES (an integer) lines of + context, or three if LINES is not given. *Note Unified Format::. + For proper operation, `patch' typically needs at least two lines of + context. + + On older systems, `diff' supports an obsolete option `-LINES' that + has effect when combined with `-u'. POSIX 1003.1-2001 (*note + Standards conformance::) does not allow this; use `-U LINES' + instead. + +`-v' +`--version' + Output version information and then exit. + +`-w' +`--ignore-all-space' + Ignore white space when comparing lines. *Note White Space::. + +`-W COLUMNS' +`--width=COLUMNS' + Output at most COLUMNS (default 130) print columns per line in + side by side format. *Note Side by Side Format::. + +`-x PATTERN' +`--exclude=PATTERN' + When comparing directories, ignore files and subdirectories whose + basenames match PATTERN. *Note Comparing Directories::. + +`-X FILE' +`--exclude-from=FILE' + When comparing directories, ignore files and subdirectories whose + basenames match any pattern contained in FILE. *Note Comparing + Directories::. + +`-y' +`--side-by-side' + Use the side by side output format. *Note Side by Side Format::. + + +File: diff.info, Node: Invoking diff3, Next: Invoking patch, Prev: Invoking diff, Up: Top + +Invoking `diff3' +**************** + + The `diff3' command compares three files and outputs descriptions of +their differences. Its arguments are as follows: + + diff3 OPTIONS... MINE OLDER YOURS + + The files to compare are MINE, OLDER, and YOURS. At most one of +these three file names may be `-', which tells `diff3' to read the +standard input for that file. + + An exit status of 0 means `diff3' was successful, 1 means some +conflicts were found, and 2 means trouble. + +* Menu: + +* diff3 Options:: Summary of options to `diff3'. + + +File: diff.info, Node: diff3 Options, Up: Invoking diff3 + +Options to `diff3' +================== + + Below is a summary of all of the options that GNU `diff3' accepts. +Multiple single letter options (unless they take an argument) can be +combined into a single command line argument. + +`-a' +`--text' + Treat all files as text and compare them line-by-line, even if they + do not appear to be text. *Note Binary::. + +`-A' +`--show-all' + Incorporate all unmerged changes from OLDER to YOURS into MINE, + surrounding conflicts with bracket lines. *Note Marking + Conflicts::. + +`--diff-program=PROGRAM' + Use the compatible comparison program PROGRAM to compare files + instead of `diff'. + +`-e' +`--ed' + Generate an `ed' script that incorporates all the changes from + OLDER to YOURS into MINE. *Note Which Changes::. + +`-E' +`--show-overlap' + Like `-e', except bracket lines from overlapping changes' first + and third files. *Note Marking Conflicts::. With `-E', an + overlapping change looks like this: + + <<<<<<< MINE + lines from MINE + ======= + lines from YOURS + >>>>>>> YOURS + +`--help' + Output a summary of usage and then exit. + +`-i' + Generate `w' and `q' commands at the end of the `ed' script for + System V compatibility. This option must be combined with one of + the `-AeExX3' options, and may not be combined with `-m'. *Note + Saving the Changed File::. + +`-L LABEL' +`--label=LABEL' + Use the label LABEL for the brackets output by the `-A', `-E' and + `-X' options. This option may be given up to three times, one for + each input file. The default labels are the names of the input + files. Thus `diff3 -L X -L Y -L Z -m A B C' acts like `diff3 -m A + B C', except that the output looks like it came from files named + `X', `Y' and `Z' rather than from files named `A', `B' and `C'. + *Note Marking Conflicts::. + +`-m' +`--merge' + Apply the edit script to the first file and send the result to + standard output. Unlike piping the output from `diff3' to `ed', + this works even for binary files and incomplete lines. `-A' is + assumed if no edit script option is specified. *Note Bypassing + ed::. + +`-T' +`--initial-tab' + Output a tab rather than two spaces before the text of a line in + normal format. This causes the alignment of tabs in the line to + look normal. *Note Tabs::. + +`-v' +`--version' + Output version information and then exit. + +`-x' +`--overlap-only' + Like `-e', except output only the overlapping changes. *Note + Which Changes::. + +`-X' + Like `-E', except output only the overlapping changes. In other + words, like `-x', except bracket changes as in `-E'. *Note + Marking Conflicts::. + +`-3' +`--easy-only' + Like `-e', except output only the nonoverlapping changes. *Note + Which Changes::. + + +File: diff.info, Node: Invoking patch, Next: Invoking sdiff, Prev: Invoking diff3, Up: Top + +Invoking `patch' +**************** + + Normally `patch' is invoked like this: + + patch <PATCHFILE + + The full format for invoking `patch' is: + + patch OPTIONS... [ORIGFILE [PATCHFILE]] + + You can also specify where to read the patch from with the `-i +PATCHFILE' or `--input=PATCHFILE' option. If you do not specify +PATCHFILE, or if PATCHFILE is `-', `patch' reads the patch (that is, +the `diff' output) from the standard input. + + If you do not specify an input file on the command line, `patch' +tries to intuit from the "leading text" (any text in the patch that +comes before the `diff' output) which file to edit. *Note Multiple +Patches::. + + By default, `patch' replaces the original input file with the +patched version, possibly after renaming the original file into a +backup file (*note Backup Names::, for a description of how `patch' +names backup files). You can also specify where to put the output with +the `-o FILE' or `--output=FILE' option; however, do not use this option +if FILE is one of the input files. + +* Menu: + +* patch Options:: Summary table of options to `patch'. + + +File: diff.info, Node: patch Options, Up: Invoking patch + +Options to `patch' +================== + + Here is a summary of all of the options that GNU `patch' accepts. +*Note patch and Tradition::, for which of these options are safe to use +in older versions of `patch'. + + Multiple single-letter options that do not take an argument can be +combined into a single command line argument with only one dash. + +`-b' +`--backup' + Back up the original contents of each file, even if backups would + normally not be made. *Note Backups::. + +`-B PREFIX' +`--prefix=PREFIX' + Prepend PREFIX to backup file names. *Note Backup Names::. + +`--backup-if-mismatch' + Back up the original contents of each file if the patch does not + exactly match the file. This is the default behavior when not + conforming to POSIX. *Note Backups::. + +`--binary' + Read and write all files in binary mode, except for standard output + and `/dev/tty'. This option has no effect on POSIX-conforming + systems like GNU/Linux. On systems where this option makes a + difference, the patch should be generated by `diff -a --binary'. + *Note Binary::. + +`-c' +`--context' + Interpret the patch file as a context diff. *Note patch Input::. + +`-d DIRECTORY' +`--directory=DIRECTORY' + Make directory DIRECTORY the current directory for interpreting + both file names in the patch file, and file names given as + arguments to other options. *Note patch Directories::. + +`-D NAME' +`--ifdef=NAME' + Make merged if-then-else output using NAME. *Note If-then-else::. + +`--dry-run' + Print the results of applying the patches without actually changing + any files. *Note Dry Runs::. + +`-e' +`--ed' + Interpret the patch file as an `ed' script. *Note patch Input::. + +`-E' +`--remove-empty-files' + Remove output files that are empty after the patches have been + applied. *Note Creating and Removing::. + +`-f' +`--force' + Assume that the user knows exactly what he or she is doing, and do + not ask any questions. *Note patch Messages::. + +`-F LINES' +`--fuzz=LINES' + Set the maximum fuzz factor to LINES. *Note Inexact::. + +`-g NUM' +`--get=NUM' + If NUM is positive, get input files from a revision control system + as necessary; if zero, do not get the files; if negative, ask the + user whether to get the files. *Note Revision Control::. + +`--help' + Output a summary of usage and then exit. + +`-i PATCHFILE' +`--input=PATCHFILE' + Read the patch from PATCHFILE rather than from standard input. + *Note patch Options::. + +`-l' +`--ignore-white-space' + Let any sequence of blanks (spaces or tabs) in the patch file match + any sequence of blanks in the input file. *Note Changed White + Space::. + +`-n' +`--normal' + Interpret the patch file as a normal diff. *Note patch Input::. + +`-N' +`--forward' + Ignore patches that `patch' thinks are reversed or already applied. + See also `-R'. *Note Reversed Patches::. + +`--no-backup-if-mismatch' + Do not back up the original contents of files. This is the default + behavior when conforming to POSIX. *Note Backups::. + +`-o FILE' +`--output=FILE' + Use FILE as the output file name. *Note patch Options::. + +`-pNUMBER' +`--strip=NUMBER' + Set the file name strip count to NUMBER. *Note patch + Directories::. + +`--posix' + Conform to POSIX, as if the `POSIXLY_CORRECT' environment variable + had been set. *Note patch and POSIX::. + +`--quoting-style=WORD' + Use style WORD to quote names in diagnostics, as if the + `QUOTING_STYLE' environment variable had been set to WORD. *Note + patch Quoting Style::. + +`-r REJECT-FILE' +`--reject-file=REJECT-FILE' + Use REJECT-FILE as the reject file name. *Note Reject Names::. + +`-R' +`--reverse' + Assume that this patch was created with the old and new files + swapped. *Note Reversed Patches::. + +`-s' +`--quiet' +`--silent' + Work silently unless an error occurs. *Note patch Messages::. + +`-t' +`--batch' + Do not ask any questions. *Note patch Messages::. + +`-T' +`--set-time' + Set the modification and access times of patched files from time + stamps given in context diff headers, assuming that the context + diff headers use local time. *Note Patching Time Stamps::. + +`-u' +`--unified' + Interpret the patch file as a unified diff. *Note patch Input::. + +`-v' +`--version' + Output version information and then exit. + +`-V BACKUP-STYLE' +`--version=control=BACKUP-STYLE' + Select the naming convention for backup file names. *Note Backup + Names::. + +`--verbose' + Print more diagnostics than usual. *Note patch Messages::. + +`-x NUMBER' +`--debug=NUMBER' + Set internal debugging flags. Of interest only to `patch' + patchers. + +`-Y PREFIX' +`--basename-prefix=PREFIX' + Prepend PREFIX to base names of backup files. *Note Backup + Names::. + +`-z SUFFIX' +`--suffix=SUFFIX' + Use SUFFIX as the backup extension instead of `.orig' or `~'. + *Note Backup Names::. + +`-Z' +`--set-utc' + Set the modification and access times of patched files from time + stamps given in context diff headers, assuming that the context + diff headers use UTC. *Note Patching Time Stamps::. + + +File: diff.info, Node: Invoking sdiff, Next: Standards conformance, Prev: Invoking patch, Up: Top + +Invoking `sdiff' +**************** + + The `sdiff' command merges two files and interactively outputs the +results. Its arguments are as follows: + + sdiff -o OUTFILE OPTIONS... FROM-FILE TO-FILE + + This merges FROM-FILE with TO-FILE, with output to OUTFILE. If +FROM-FILE is a directory and TO-FILE is not, `sdiff' compares the file +in FROM-FILE whose file name is that of TO-FILE, and vice versa. +FROM-FILE and TO-FILE may not both be directories. + + `sdiff' options begin with `-', so normally FROM-FILE and TO-FILE +may not begin with `-'. However, `--' as an argument by itself treats +the remaining arguments as file names even if they begin with `-'. You +may not use `-' as an input file. + + `sdiff' without `-o' (or `--output') produces a side-by-side +difference. This usage is obsolete; use the `-y' or `--side-by-side' +option of `diff' instead. + + An exit status of 0 means no differences were found, 1 means some +differences were found, and 2 means trouble. + +* Menu: + +* sdiff Options:: Summary of options to `diff'. + + +File: diff.info, Node: sdiff Options, Up: Invoking sdiff + +Options to `sdiff' +================== + + Below is a summary of all of the options that GNU `sdiff' accepts. +Each option has two equivalent names, one of which is a single letter +preceded by `-', and the other of which is a long name preceded by +`--'. Multiple single letter options (unless they take an argument) +can be combined into a single command line argument. Long named +options can be abbreviated to any unique prefix of their name. + +`-a' +`--text' + Treat all files as text and compare them line-by-line, even if they + do not appear to be text. *Note Binary::. + +`-b' +`--ignore-space-change' + Ignore changes in amount of white space. *Note White Space::. + +`-B' +`--ignore-blank-lines' + Ignore changes that just insert or delete blank lines. *Note + Blank Lines::. + +`-d' +`--minimal' + Change the algorithm to perhaps find a smaller set of changes. + This makes `sdiff' slower (sometimes much slower). *Note diff + Performance::. + +`--diff-program=PROGRAM' + Use the compatible comparison program PROGRAM to compare files + instead of `diff'. + +`-E' +`--ignore-tab-expansion' + Ignore changes due to tab expansion. *Note White Space::. + +`--help' + Output a summary of usage and then exit. + +`-i' +`--ignore-case' + Ignore changes in case; consider upper- and lower-case to be the + same. *Note Case Folding::. + +`-I REGEXP' +`--ignore-matching-lines=REGEXP' + Ignore changes that just insert or delete lines that match REGEXP. + *Note Specified Folding::. + +`-l' +`--left-column' + Print only the left column of two common lines. *Note Side by + Side Format::. + +`-o FILE' +`--output=FILE' + Put merged output into FILE. This option is required for merging. + +`-s' +`--suppress-common-lines' + Do not print common lines. *Note Side by Side Format::. + +`--speed-large-files' + Use heuristics to speed handling of large files that have numerous + scattered small changes. *Note diff Performance::. + +`--strip-trailing-cr' + Strip any trailing carriage return at the end of an input line. + *Note Binary::. + +`-t' +`--expand-tabs' + Expand tabs to spaces in the output, to preserve the alignment of + tabs in the input files. *Note Tabs::. + +`-v' +`--version' + Output version information and then exit. + +`-w COLUMNS' +`--width=COLUMNS' + Output at most COLUMNS (default 130) print columns per line. + *Note Side by Side Format::. Note that for historical reasons, + this option is `-W' in `diff', `-w' in `sdiff'. + +`-W' +`--ignore-all-space' + Ignore white space when comparing lines. *Note White Space::. + Note that for historical reasons, this option is `-w' in `diff', + `-W' in `sdiff'. + + +File: diff.info, Node: Standards conformance, Next: Projects, Prev: Invoking sdiff, Up: Top + +Standards conformance +********************* + + In a few cases, the GNU utilities' default behavior is incompatible +with the POSIX standard. To suppress these incompatibilities, define +the `POSIXLY_CORRECT' environment variable. Unless you are checking +for POSIX conformance, you probably do not need to define +`POSIXLY_CORRECT'. + + Normally options and operands can appear in any order, and programs +act as if all the options appear before any operands. For example, +`diff lao tzu -C 2' acts like `diff -C 2 lao tzu', since `2' is an +option-argument of `-C'. However, if the `POSIXLY_CORRECT' environment +variable is set, options must appear before operands, unless otherwise +specified for a particular command. + + Newer versions of POSIX are occasionally incompatible with older +versions. For example, older versions of POSIX allowed the command +`diff -c -10' to have the same meaning as `diff -C 10', but POSIX +1003.1-2001 `diff' no longer allows digit-string options like `-10'. + + The GNU utilities normally conform to the version of POSIX that is +standard for your system. To cause them to conform to a different +version of POSIX, define the `_POSIX2_VERSION' environment variable to +a value of the form YYYYMM specifying the year and month the standard +was adopted. Two values are currently supported for `_POSIX2_VERSION': +`199209' stands for POSIX 1003.2-1992, and `200112' stands for POSIX +1003.1-2001. For example, if you are running older software that +assumes an older version of POSIX and uses `diff -c -10', you can work +around the compatibility problems by setting `_POSIX2_VERSION=199209' +in your environment. + + +File: diff.info, Node: Projects, Next: Copying This Manual, Prev: Standards conformance, Up: Top + +Future Projects +*************** + + Here are some ideas for improving GNU `diff' and `patch'. The GNU +project has identified some improvements as potential programming +projects for volunteers. You can also help by reporting any bugs that +you find. + + If you are a programmer and would like to contribute something to the +GNU project, please consider volunteering for one of these projects. +If you are seriously contemplating work, please write to <gnu@gnu.org> +to coordinate with other volunteers. + +* Menu: + +* Shortcomings:: Suggested projects for improvements. +* Bugs:: Reporting bugs. + + +File: diff.info, Node: Shortcomings, Next: Bugs, Up: Projects + +Suggested Projects for Improving GNU `diff' and `patch' +======================================================= + + One should be able to use GNU `diff' to generate a patch from any +pair of directory trees, and given the patch and a copy of one such +tree, use `patch' to generate a faithful copy of the other. +Unfortunately, some changes to directory trees cannot be expressed using +current patch formats; also, `patch' does not handle some of the +existing formats. These shortcomings motivate the following suggested +projects. + +* Menu: + +* Internationalization:: Handling multibyte and varying-width characters. +* Changing Structure:: Handling changes to the directory structure. +* Special Files:: Handling symbolic links, device special files, etc. +* Unusual File Names:: Handling file names that contain unusual characters. +* Time Stamp Order:: Outputting diffs in time stamp order. +* Ignoring Changes:: Ignoring certain changes while showing others. +* Speedups:: Improving performance. + + +File: diff.info, Node: Internationalization, Next: Changing Structure, Up: Shortcomings + +Handling Multibyte and Varying-Width Characters +----------------------------------------------- + + `diff', `diff3' and `sdiff' treat each line of input as a string of +unibyte characters. This can mishandle multibyte characters in some +cases. For example, when asked to ignore spaces, `diff' does not +properly ignore a multibyte space character. + + Also, `diff' currently assumes that each byte is one column wide, +and this assumption is incorrect in some locales, e.g., locales that +use UTF-8 encoding. This causes problems with the `-y' or +`--side-by-side' option of `diff'. + + These problems need to be fixed without unduly affecting the +performance of the utilities in unibyte environments. + + The IBM GNU/Linux Technology Center Internationalization Team has +proposed some patches to support internationalized `diff' +`http://oss.software.ibm.com/developer/opensource/linux/patches/i18n/diffutils-2.7.2-i18n-0.1.patch.gz'. +Unfortunately, these patches are incomplete and are to an older version +of `diff', so more work needs to be done in this area. + + +File: diff.info, Node: Changing Structure, Next: Special Files, Prev: Internationalization, Up: Shortcomings + +Handling Changes to the Directory Structure +------------------------------------------- + + `diff' and `patch' do not handle some changes to directory +structure. For example, suppose one directory tree contains a directory +named `D' with some subsidiary files, and another contains a file with +the same name `D'. `diff -r' does not output enough information for +`patch' to transform the directory subtree into the file. + + There should be a way to specify that a file has been removed without +having to include its entire contents in the patch file. There should +also be a way to tell `patch' that a file was renamed, even if there is +no way for `diff' to generate such information. There should be a way +to tell `patch' that a file's time stamp has changed, even if its +contents have not changed. + + These problems can be fixed by extending the `diff' output format to +represent changes in directory structure, and extending `patch' to +understand these extensions. + + +File: diff.info, Node: Special Files, Next: Unusual File Names, Prev: Changing Structure, Up: Shortcomings + +Files that are Neither Directories Nor Regular Files +---------------------------------------------------- + + Some files are neither directories nor regular files: they are +unusual files like symbolic links, device special files, named pipes, +and sockets. Currently, `diff' treats symbolic links like regular +files; it treats other special files like regular files if they are +specified at the top level, but simply reports their presence when +comparing directories. This means that `patch' cannot represent changes +to such files. For example, if you change which file a symbolic link +points to, `diff' outputs the difference between the two files, instead +of the change to the symbolic link. + + `diff' should optionally report changes to special files specially, +and `patch' should be extended to understand these extensions. + + +File: diff.info, Node: Unusual File Names, Next: Time Stamp Order, Prev: Special Files, Up: Shortcomings + +File Names that Contain Unusual Characters +------------------------------------------ + + When a file name contains an unusual character like a newline or +white space, `diff -r' generates a patch that `patch' cannot parse. +The problem is with format of `diff' output, not just with `patch', +because with odd enough file names one can cause `diff' to generate a +patch that is syntactically correct but patches the wrong files. The +format of `diff' output should be extended to handle all possible file +names. + + +File: diff.info, Node: Time Stamp Order, Next: Ignoring Changes, Prev: Unusual File Names, Up: Shortcomings + +Outputting Diffs in Time Stamp Order +------------------------------------ + + Applying `patch' to a multiple-file diff can result in files whose +time stamps are out of order. GNU `patch' has options to restore the +time stamps of the updated files (*note Patching Time Stamps::), but +sometimes it is useful to generate a patch that works even if the +recipient does not have GNU patch, or does not use these options. One +way to do this would be to implement a `diff' option to output diffs in +time stamp order. + + +File: diff.info, Node: Ignoring Changes, Next: Speedups, Prev: Time Stamp Order, Up: Shortcomings + +Ignoring Certain Changes +------------------------ + + It would be nice to have a feature for specifying two strings, one in +FROM-FILE and one in TO-FILE, which should be considered to match. +Thus, if the two strings are `foo' and `bar', then if two lines differ +only in that `foo' in file 1 corresponds to `bar' in file 2, the lines +are treated as identical. + + It is not clear how general this feature can or should be, or what +syntax should be used for it. + + A partial substitute is to filter one or both files before comparing, +e.g.: + + sed 's/foo/bar/g' file1 | diff - file2 + + However, this outputs the filtered text, not the original. + + +File: diff.info, Node: Speedups, Prev: Ignoring Changes, Up: Shortcomings + +Improving Performance +--------------------- + + When comparing two large directory structures, one of which was +originally copied from the other with time stamps preserved (e.g., with +`cp -pR'), it would greatly improve performance if an option told +`diff' to assume that two files with the same size and time stamps have +the same content. *Note diff Performance::. + + +File: diff.info, Node: Bugs, Prev: Shortcomings, Up: Projects + +Reporting Bugs +============== + + If you think you have found a bug in GNU `cmp', `diff', `diff3', or +`sdiff', please report it by electronic mail to the GNU utilities bug +report mailing list +(http://mail.gnu.org/mailman/listinfo/bug-gnu-utils) +<bug-gnu-utils@gnu.org>. Please send bug reports for GNU `patch' to +<bug-patch@gnu.org>. Send as precise a description of the problem as +you can, including the output of the `--version' option and sample +input files that produce the bug, if applicable. If you have a +nontrivial fix for the bug, please send it as well. If you have a +patch, please send it too. It may simplify the maintainer's job if the +patch is relative to a recent test release, which you can find in the +directory `ftp://alpha.gnu.org/gnu/diffutils/'. + + +File: diff.info, Node: Copying This Manual, Next: Index, Prev: Projects, Up: Top + +Copying This Manual +******************* + +* Menu: + +* GNU Free Documentation License:: License for copying this manual. + + +File: diff.info, Node: GNU Free Documentation License, Up: Copying This Manual + +GNU Free Documentation License +============================== + + Version 1.1, March 2000 + Copyright (C) 2000 Free Software Foundation, Inc. + 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA + + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + 0. PREAMBLE + + The purpose of this License is to make a manual, textbook, or other + written document "free" in the sense of freedom: to assure everyone + the effective freedom to copy and redistribute it, with or without + modifying it, either commercially or noncommercially. Secondarily, + this License preserves for the author and publisher a way to get + credit for their work, while not being considered responsible for + modifications made by others. + + This License is a kind of "copyleft", which means that derivative + works of the document must themselves be free in the same sense. + It complements the GNU General Public License, which is a copyleft + license designed for free software. + + We have designed this License in order to use it for manuals for + free software, because free software needs free documentation: a + free program should come with manuals providing the same freedoms + that the software does. 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If + the Document does not specify a version number of this License, + you may choose any version ever published (not as a draft) by the + Free Software Foundation. + +ADDENDUM: How to use this License for your documents +---------------------------------------------------- + + To use this License in a document you have written, include a copy of +the License in the document and put the following copyright and license +notices just after the title page: + + Copyright (C) YEAR YOUR NAME. + Permission is granted to copy, distribute and/or modify this document + under the terms of the GNU Free Documentation License, Version 1.1 + or any later version published by the Free Software Foundation; + with the Invariant Sections being LIST THEIR TITLES, with the + Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. + A copy of the license is included in the section entitled ``GNU + Free Documentation License''. + + If you have no Invariant Sections, write "with no Invariant Sections" +instead of saying which ones are invariant. If you have no Front-Cover +Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being +LIST"; likewise for Back-Cover Texts. + + If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, to +permit their use in free software. + + +File: diff.info, Node: Index, Prev: Copying This Manual, Up: Top + +Index +***** + +* Menu: + +* ! output format: Context. +* +- output format: Unified Format. +* < output format: Normal. +* <<<<<<< for marking conflicts: Marking Conflicts. +* _POSIX2_VERSION: Standards conformance. +* aligning tab stops: Tabs. +* alternate file names: Alternate Names. +* backup file names: Backup Names. +* backup file strategy: Backups. +* binary file diff: Binary. +* blank and tab difference suppression: White Space. +* blank line difference suppression: Blank Lines. +* brief difference reports: Brief. +* bug reports: Bugs. +* C function headings: C Function Headings. +* C if-then-else output format: If-then-else. +* case difference suppression: Case Folding. +* ClearCase: Revision Control. +* cmp invocation: Invoking cmp. +* cmp options: cmp Options. +* columnar output: Side by Side. +* common mistakes with patches: Avoiding Common Mistakes. +* comparing three files: Comparing Three Files. +* conflict: diff3 Merging. +* conflict marking: Marking Conflicts. +* context output format: Context. +* creating files: Creating and Removing. +* diagnostics from patch: patch Messages. +* diff invocation: Invoking diff. +* diff merging: Interactive Merging. +* diff options: diff Options. +* diff sample input: Sample diff Input. +* diff3 hunks: diff3 Hunks. +* diff3 invocation: Invoking diff3. +* diff3 options: diff3 Options. +* diff3 sample input: Sample diff3 Input. +* directories and patch: patch Directories. +* directory structure changes: Changing Structure. +* dry runs for patch: Dry Runs. +* ed script output format: ed Scripts. +* EDITOR: Merge Commands. +* empty files, removing: Creating and Removing. +* exabyte, definition of: cmp Options. +* exbibyte, definition of: cmp Options. +* FDL, GNU Free Documentation License: GNU Free Documentation License. +* file name alternates: Alternate Names. +* file names with unusual characters: Unusual File Names. +* format of diff output: Output Formats. +* format of diff3 output: Comparing Three Files. +* formats for if-then-else line groups: Line Group Formats. +* forward ed script output format: Forward ed. +* full lines: Incomplete Lines. +* function headings, C: C Function Headings. +* fuzz factor when patching: Inexact. +* gibibyte, definition of: cmp Options. +* gigabyte, definition of: cmp Options. +* headings: Sections. +* hunks: Hunks. +* hunks for diff3: diff3 Hunks. +* if-then-else output format: If-then-else. +* ifdef output format: If-then-else. +* imperfect patch application: Imperfect. +* incomplete line merging: Merging Incomplete Lines. +* incomplete lines: Incomplete Lines. +* inexact patches: Inexact. +* inhibit messages from patch: More or Fewer Messages. +* interactive merging: Interactive Merging. +* introduction: Comparison. +* intuiting file names from patches: Multiple Patches. +* invoking cmp: Invoking cmp. +* invoking diff: Invoking diff. +* invoking diff3: Invoking diff3. +* invoking patch: Invoking patch. +* invoking sdiff: Invoking sdiff. +* keyboard input to patch: patch and Keyboard Input. +* kibibyte, definition of: cmp Options. +* kilobyte, definition of: cmp Options. +* LC_COLLATE: Comparing Directories. +* LC_NUMERIC: Line Group Formats. +* LC_TIME: Detailed Context. +* line formats: Line Formats. +* line group formats: Line Group Formats. +* mebibyte, definition of: cmp Options. +* megabyte, definition of: cmp Options. +* merge commands: Merge Commands. +* merged diff3 format: Bypassing ed. +* merged output format: If-then-else. +* merging from a common ancestor: diff3 Merging. +* merging interactively: Merge Commands. +* messages from patch: patch Messages. +* multibyte characters: Internationalization. +* multiple patches: Multiple Patches. +* newline treatment by diff: Incomplete Lines. +* normal output format: Normal. +* options for cmp: cmp Options. +* options for diff: diff Options. +* options for diff3: diff3 Options. +* options for patch: patch Options. +* options for sdiff: sdiff Options. +* output formats: Output Formats. +* overlap: diff3 Merging. +* overlapping change, selection of: Which Changes. +* overview of diff and patch: Overview. +* paginating diff output: Pagination. +* patch consumer tips: Tips for Patch Consumers. +* patch input format: patch Input. +* patch invocation: Invoking patch. +* patch messages and questions: patch Messages. +* patch options: patch Options. +* patch producer tips: Tips for Patch Producers. +* patch, common mistakes: Avoiding Common Mistakes. +* PATCH_GET: Revision Control. +* PATCH_VERSION_CONTROL: Backup Names. +* patches, shrinking: Generating Smaller Patches. +* patching directories: patch Directories. +* pebibyte, definition of: cmp Options. +* performance of diff: diff Performance. +* petabyte, definition of: cmp Options. +* POSIX <1>: Standards conformance. +* POSIX: patch and POSIX. +* POSIXLY_CORRECT <1>: patch and POSIX. +* POSIXLY_CORRECT: Standards conformance. +* projects for directories: Shortcomings. +* quoting style: patch Quoting Style. +* QUOTING_STYLE: patch Quoting Style. +* RCS: Revision Control. +* RCS script output format: RCS. +* regular expression matching headings: Specified Headings. +* regular expression suppression: Specified Folding. +* reject file names: Reject Names. +* removing empty files: Creating and Removing. +* reporting bugs: Bugs. +* reversed patches: Reversed Patches. +* revision control: Revision Control. +* sample input for diff: Sample diff Input. +* sample input for diff3: Sample diff3 Input. +* SCCS: Revision Control. +* script output formats: Scripts. +* sdiff invocation: Invoking sdiff. +* sdiff options: sdiff Options. +* sdiff output format: sdiff Option Summary. +* section headings: Sections. +* side by side: Side by Side. +* side by side format: Side by Side Format. +* SIMPLE_BACKUP_SUFFIX: Backup Names. +* special files: Special Files. +* specified headings: Specified Headings. +* summarizing which files differ: Brief. +* System V diff3 compatibility: Saving the Changed File. +* tab and blank difference suppression: White Space. +* tab stop alignment: Tabs. +* tebibyte, definition of: cmp Options. +* terabyte, definition of: cmp Options. +* testing patch: Dry Runs. +* text versus binary diff: Binary. +* time stamp format, context diffs: Detailed Context. +* time stamp format, unified diffs: Detailed Unified. +* time stamps on patched files: Patching Time Stamps. +* traditional patch: patch and Tradition. +* two-column output: Side by Side. +* unified output format: Unified Format. +* unmerged change: Which Changes. +* varying-width characters: Internationalization. +* verbose messages from patch: More or Fewer Messages. +* version control: Revision Control. +* VERSION_CONTROL <1>: Backup Names. +* VERSION_CONTROL: Revision Control. +* white space in patches: Changed White Space. +* yottabyte, definition of: cmp Options. +* zettabyte, definition of: cmp Options. + + + +Tag Table: +Node: Top1653 +Node: Overview4045 +Node: Comparison7202 +Node: Hunks9888 +Node: White Space11313 +Node: Blank Lines12807 +Node: Case Folding13562 +Node: Specified Folding13977 +Node: Brief15052 +Node: Binary16295 +Node: Output Formats20358 +Node: Sample diff Input21076 +Node: Normal22569 +Node: Detailed Normal23564 +Node: Example Normal25289 +Node: Context26011 +Node: Context Format27567 +Node: Detailed Context28345 +Node: Example Context30234 +Node: Less Context31748 +Node: Unified Format32894 +Node: Detailed Unified33676 +Node: Example Unified34787 +Node: Sections35807 +Node: Specified Headings36552 +Node: C Function Headings38083 +Node: Alternate Names38908 +Node: Side by Side39808 +Node: Side by Side Format41947 +Node: Example Side by Side42836 +Node: Scripts44162 +Node: ed Scripts44563 +Node: Detailed ed45756 +Node: Example ed47497 +Node: Forward ed47934 +Node: RCS48696 +Node: If-then-else49904 +Node: Line Group Formats51572 +Node: Line Formats57437 +Node: Detailed If-then-else60693 +Node: Example If-then-else62583 +Node: Incomplete Lines63632 +Node: Comparing Directories65263 +Node: Adjusting Output69220 +Node: Tabs69645 +Node: Pagination71177 +Node: diff Performance71626 +Node: Comparing Three Files74708 +Node: Sample diff3 Input75580 +Node: Detailed diff3 Normal76528 +Node: diff3 Hunks78307 +Node: Example diff3 Normal79593 +Node: diff3 Merging80616 +Node: Which Changes82854 +Node: Marking Conflicts84258 +Node: Bypassing ed86714 +Node: Merging Incomplete Lines88068 +Node: Saving the Changed File88784 +Node: Interactive Merging89390 +Node: sdiff Option Summary90094 +Node: Merge Commands91242 +Node: Merging with patch92503 +Node: patch Input94867 +Node: Revision Control95537 +Node: Imperfect96689 +Node: Changed White Space97825 +Node: Reversed Patches98606 +Node: Inexact100056 +Node: Dry Runs103599 +Node: Creating and Removing104447 +Node: Patching Time Stamps105486 +Node: Multiple Patches107677 +Node: patch Directories110328 +Node: Backups111942 +Node: Backup Names112996 +Ref: Backup Names-Footnote-1115955 +Node: Reject Names116082 +Node: patch Messages116660 +Node: More or Fewer Messages117706 +Node: patch and Keyboard Input118319 +Node: patch Quoting Style119332 +Node: patch and POSIX120464 +Node: patch and Tradition121290 +Node: Making Patches124734 +Node: Tips for Patch Producers125552 +Node: Tips for Patch Consumers126796 +Node: Avoiding Common Mistakes127421 +Node: Generating Smaller Patches129934 +Node: Invoking cmp131683 +Node: cmp Options132532 +Node: Invoking diff135896 +Node: diff Options137599 +Node: Invoking diff3145722 +Node: diff3 Options146352 +Node: Invoking patch149255 +Node: patch Options150455 +Node: Invoking sdiff155669 +Node: sdiff Options156808 +Node: Standards conformance159561 +Node: Projects161299 +Node: Shortcomings162002 +Node: Internationalization163092 +Node: Changing Structure164247 +Node: Special Files165336 +Node: Unusual File Names166282 +Node: Time Stamp Order166904 +Node: Ignoring Changes167531 +Node: Speedups168285 +Node: Bugs168733 +Node: Copying This Manual169574 +Node: GNU Free Documentation License169782 +Node: Index189646 + +End Tag Table diff --git a/external/gpl2/diffutils/dist/doc/diff.texi b/external/gpl2/diffutils/dist/doc/diff.texi new file mode 100644 index 00000000000..63537a65935 --- /dev/null +++ b/external/gpl2/diffutils/dist/doc/diff.texi @@ -0,0 +1,4557 @@ +\input texinfo @c -*-texinfo-*- +@c $NetBSD: diff.texi,v 1.1.1.1 2016/01/13 03:15:29 christos Exp $ +@comment Id +@comment %**start of header +@setfilename diff.info +@include version.texi +@settitle Comparing and Merging Files +@syncodeindex vr cp +@setchapternewpage odd +@comment %**end of header +@copying +This manual is for GNU Diffutils +(version @value{VERSION}, @value{UPDATED}), +and documents the @sc{gnu} @command{diff}, @command{diff3}, +@command{sdiff}, and @command{cmp} commands for showing the +differences between files and the @sc{gnu} @command{patch} command for +using their output to update files. + +Copyright @copyright{} 1992, 1993, 1994, 1998, 2001, 2002 Free +Software Foundation, Inc. + +@quotation +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.1 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with the Front-Cover texts being ``A GNU Manual,'' +and with the Back-Cover Texts as in (a) below. A copy of the +license is included in the section entitled ``GNU Free Documentation +License.'' + +(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify +this GNU Manual, like GNU software. Copies published by the Free +Software Foundation raise funds for GNU development.'' +@end quotation +@end copying + +@c Debian install-info (up through at least version 1.9.20) uses only the +@c first dircategory. Put this one first, as it is more useful in practice. +@dircategory Individual utilities +@direntry +* cmp: (diff)Invoking cmp. Compare 2 files byte by byte. +* diff: (diff)Invoking diff. Compare 2 files line by line. +* diff3: (diff)Invoking diff3. Compare 3 files line by line. +* patch: (diff)Invoking patch. Apply a patch to a file. +* sdiff: (diff)Invoking sdiff. Merge 2 files side-by-side. +@end direntry + +@dircategory GNU packages +@direntry +* Diff: (diff). Comparing and merging files. +@end direntry + +@titlepage +@title Comparing and Merging Files +@subtitle for Diffutils @value{VERSION} and @code{patch} 2.5.4 +@subtitle @value{UPDATED} +@author David MacKenzie, Paul Eggert, and Richard Stallman +@page +@vskip 0pt plus 1filll +@insertcopying +@end titlepage + +@shortcontents +@contents + +@ifnottex +@node Top +@top Comparing and Merging Files + +@insertcopying +@end ifnottex + +@menu +* Overview:: Preliminary information. +* Comparison:: What file comparison means. + +* Output Formats:: Formats for two-way difference reports. +* Incomplete Lines:: Lines that lack trailing newlines. +* Comparing Directories:: Comparing files and directories. +* Adjusting Output:: Making @command{diff} output prettier. +* diff Performance:: Making @command{diff} smarter or faster. + +* Comparing Three Files:: Formats for three-way difference reports. +* diff3 Merging:: Merging from a common ancestor. + +* Interactive Merging:: Interactive merging with @command{sdiff}. + +* Merging with patch:: Using @command{patch} to change old files into new ones. +* Making Patches:: Tips for making and using patch distributions. + +* Invoking cmp:: Compare two files byte by byte. +* Invoking diff:: Compare two files line by line. +* Invoking diff3:: Compare three files line by line. +* Invoking patch:: Apply a diff file to an original. +* Invoking sdiff:: Side-by-side merge of file differences. + +* Standards conformance:: Conformance to the @sc{posix} standard. +* Projects:: If you've found a bug or other shortcoming. + +* Copying This Manual:: How to make copies of this manual. +* Index:: Index. +@end menu + +@node Overview +@unnumbered Overview +@cindex overview of @command{diff} and @command{patch} + +Computer users often find occasion to ask how two files differ. Perhaps +one file is a newer version of the other file. Or maybe the two files +started out as identical copies but were changed by different people. + +You can use the @command{diff} command to show differences between two +files, or each corresponding file in two directories. @command{diff} +outputs differences between files line by line in any of several +formats, selectable by command line options. This set of differences is +often called a @dfn{diff} or @dfn{patch}. For files that are identical, +@command{diff} normally produces no output; for binary (non-text) files, +@command{diff} normally reports only that they are different. + +You can use the @command{cmp} command to show the byte and line numbers +where two files differ. @command{cmp} can also show all the bytes +that differ between the two files, side by side. A way to compare +two files character by character is the Emacs command @kbd{M-x +compare-windows}. @xref{Other Window, , Other Window, emacs, The @sc{gnu} +Emacs Manual}, for more information on that command. + +You can use the @command{diff3} command to show differences among three +files. When two people have made independent changes to a common +original, @command{diff3} can report the differences between the original +and the two changed versions, and can produce a merged file that +contains both persons' changes together with warnings about conflicts. + +You can use the @command{sdiff} command to merge two files interactively. + +You can use the set of differences produced by @command{diff} to distribute +updates to text files (such as program source code) to other people. +This method is especially useful when the differences are small compared +to the complete files. Given @command{diff} output, you can use the +@command{patch} program to update, or @dfn{patch}, a copy of the file. If you +think of @command{diff} as subtracting one file from another to produce +their difference, you can think of @command{patch} as adding the difference +to one file to reproduce the other. + +This manual first concentrates on making diffs, and later shows how to +use diffs to update files. + +@sc{gnu} @command{diff} was written by Paul Eggert, Mike Haertel, +David Hayes, Richard Stallman, and Len Tower. Wayne Davison designed and +implemented the unified output format. The basic algorithm is described +in ``An O(ND) Difference Algorithm and its Variations'', Eugene W. Myers, +@cite{Algorithmica} Vol.@: 1 No.@: 2, 1986, pp.@: 251--266; and in ``A File +Comparison Program'', Webb Miller and Eugene W. Myers, +@cite{Software---Practice and Experience} Vol.@: 15 No.@: 11, 1985, +pp.@: 1025--1040. +@c From: "Gene Myers" <gene@cs.arizona.edu> +@c They are about the same basic algorithm; the Algorithmica +@c paper gives a rigorous treatment and the sub-algorithm for +@c delivering scripts and should be the primary reference, but +@c both should be mentioned. +The algorithm was independently discovered as described in +``Algorithms for Approximate String Matching'', +E. Ukkonen, @cite{Information and Control} Vol.@: 64, 1985, pp.@: 100--118. +@c From: "Gene Myers" <gene@cs.arizona.edu> +@c Date: Wed, 29 Sep 1993 08:27:55 MST +@c Ukkonen should be given credit for also discovering the algorithm used +@c in GNU diff. + +@sc{gnu} @command{diff3} was written by Randy Smith. @sc{gnu} +@command{sdiff} was written by Thomas Lord. @sc{gnu} @command{cmp} +was written by Torbjorn Granlund and David MacKenzie. + +@command{patch} was written mainly by Larry Wall and Paul Eggert; +several @sc{gnu} enhancements were contributed by Wayne Davison and +David MacKenzie. Parts of this manual are adapted from a manual page +written by Larry Wall, with his permission. + +@node Comparison +@chapter What Comparison Means +@cindex introduction + +There are several ways to think about the differences between two files. +One way to think of the differences is as a series of lines that were +deleted from, inserted in, or changed in one file to produce the other +file. @command{diff} compares two files line by line, finds groups of +lines that differ, and reports each group of differing lines. It can +report the differing lines in several formats, which have different +purposes. + +@sc{gnu} @command{diff} can show whether files are different without detailing +the differences. It also provides ways to suppress certain kinds of +differences that are not important to you. Most commonly, such +differences are changes in the amount of white space between words or +lines. @command{diff} also provides ways to suppress differences in +alphabetic case or in lines that match a regular expression that you +provide. These options can accumulate; for example, you can ignore +changes in both white space and alphabetic case. + +Another way to think of the differences between two files is as a +sequence of pairs of bytes that can be either identical or +different. @command{cmp} reports the differences between two files +byte by byte, instead of line by line. As a result, it is often +more useful than @command{diff} for comparing binary files. For text +files, @command{cmp} is useful mainly when you want to know only whether +two files are identical, or whether one file is a prefix of the other. + +To illustrate the effect that considering changes byte by byte +can have compared with considering them line by line, think of what +happens if a single newline character is added to the beginning of a +file. If that file is then compared with an otherwise identical file +that lacks the newline at the beginning, @command{diff} will report that a +blank line has been added to the file, while @command{cmp} will report that +almost every byte of the two files differs. + +@command{diff3} normally compares three input files line by line, finds +groups of lines that differ, and reports each group of differing lines. +Its output is designed to make it easy to inspect two different sets of +changes to the same file. + +@menu +* Hunks:: Groups of differing lines. +* White Space:: Suppressing differences in white space. +* Blank Lines:: Suppressing differences in blank lines. +* Case Folding:: Suppressing differences in alphabetic case. +* Specified Folding:: Suppressing differences that match regular expressions. +* Brief:: Summarizing which files are different. +* Binary:: Comparing binary files or forcing text comparisons. +@end menu + +@node Hunks +@section Hunks +@cindex hunks + +When comparing two files, @command{diff} finds sequences of lines common to +both files, interspersed with groups of differing lines called +@dfn{hunks}. Comparing two identical files yields one sequence of +common lines and no hunks, because no lines differ. Comparing two +entirely different files yields no common lines and one large hunk that +contains all lines of both files. In general, there are many ways to +match up lines between two given files. @command{diff} tries to minimize +the total hunk size by finding large sequences of common lines +interspersed with small hunks of differing lines. + +For example, suppose the file @file{F} contains the three lines +@samp{a}, @samp{b}, @samp{c}, and the file @file{G} contains the same +three lines in reverse order @samp{c}, @samp{b}, @samp{a}. If +@command{diff} finds the line @samp{c} as common, then the command +@samp{diff F G} produces this output: + +@example +1,2d0 +< a +< b +3a2,3 +> b +> a +@end example + +@noindent +But if @command{diff} notices the common line @samp{b} instead, it produces +this output: + +@example +1c1 +< a +--- +> c +3c3 +< c +--- +> a +@end example + +@noindent +It is also possible to find @samp{a} as the common line. @command{diff} +does not always find an optimal matching between the files; it takes +shortcuts to run faster. But its output is usually close to the +shortest possible. You can adjust this tradeoff with the +@option{--minimal} option (@pxref{diff Performance}). + +@node White Space +@section Suppressing Differences in Blank and Tab Spacing +@cindex blank and tab difference suppression +@cindex tab and blank difference suppression + +The @option{-E} and @option{--ignore-tab-expansion} options ignore the +distinction between tabs and spaces on input. A tab is considered to be +equivalent to the number of spaces to the next tab stop. @command{diff} +assumes that tab stops are set every 8 print columns. + +The @option{-b} and @option{--ignore-space-change} options are stronger. +They ignore white space at line end, and consider all other sequences of +one or more white space characters to be equivalent. With these +options, @command{diff} considers the following two lines to be equivalent, +where @samp{$} denotes the line end: + +@example +Here lyeth muche rychnesse in lytell space. -- John Heywood$ +Here lyeth muche rychnesse in lytell space. -- John Heywood $ +@end example + +The @option{-w} and @option{--ignore-all-space} options are stronger still. +They ignore difference even if one line has white space where +the other line has none. @dfn{White space} characters include +tab, newline, vertical tab, form feed, carriage return, and space; +some locales may define additional characters to be white space. +With these options, @command{diff} considers the +following two lines to be equivalent, where @samp{$} denotes the line +end and @samp{^M} denotes a carriage return: + +@example +Here lyeth muche rychnesse in lytell space.-- John Heywood$ + He relyeth much erychnes seinly tells pace. --John Heywood ^M$ +@end example + +@node Blank Lines +@section Suppressing Differences in Blank Lines +@cindex blank line difference suppression + +The @option{-B} and @option{--ignore-blank-lines} options ignore insertions +or deletions of blank lines. These options affect only lines +that are completely empty; they do not affect lines that look empty but +contain space or tab characters. With these options, for example, a +file containing +@example +1. A point is that which has no part. + +2. A line is breadthless length. +-- Euclid, The Elements, I +@end example +@noindent +is considered identical to a file containing +@example +1. A point is that which has no part. +2. A line is breadthless length. + + +-- Euclid, The Elements, I +@end example + +@node Case Folding +@section Suppressing Case Differences +@cindex case difference suppression + +@sc{gnu} @command{diff} can treat lower case letters as equivalent to their +upper case counterparts, so that, for example, it considers @samp{Funky +Stuff}, @samp{funky STUFF}, and @samp{fUNKy stuFf} to all be the same. +To request this, use the @option{-i} or @option{--ignore-case} option. + +@node Specified Folding +@section Suppressing Lines Matching a Regular Expression +@cindex regular expression suppression + +To ignore insertions and deletions of lines that match a +@command{grep}-style regular expression, use the @option{-I +@var{regexp}} or @option{--ignore-matching-lines=@var{regexp}} option. +You should escape +regular expressions that contain shell metacharacters to prevent the +shell from expanding them. For example, @samp{diff -I '^[[:digit:]]'} ignores +all changes to lines beginning with a digit. + +However, @option{-I} only ignores the insertion or deletion of lines that +contain the regular expression if every changed line in the hunk---every +insertion and every deletion---matches the regular expression. In other +words, for each nonignorable change, @command{diff} prints the complete set +of changes in its vicinity, including the ignorable ones. + +You can specify more than one regular expression for lines to ignore by +using more than one @option{-I} option. @command{diff} tries to match each +line against each regular expression. + +@node Brief +@section Summarizing Which Files Differ +@cindex summarizing which files differ +@cindex brief difference reports + +When you only want to find out whether files are different, and you +don't care what the differences are, you can use the summary output +format. In this format, instead of showing the differences between the +files, @command{diff} simply reports whether files differ. The @option{-q} +and @option{--brief} options select this output format. + +This format is especially useful when comparing the contents of two +directories. It is also much faster than doing the normal line by line +comparisons, because @command{diff} can stop analyzing the files as soon as +it knows that there are any differences. + +You can also get a brief indication of whether two files differ by using +@command{cmp}. For files that are identical, @command{cmp} produces no +output. When the files differ, by default, @command{cmp} outputs the byte +and line number where the first difference occurs. You can use +the @option{-s} option to suppress that information, so that @command{cmp} +produces no output and reports whether the files differ using only its +exit status (@pxref{Invoking cmp}). + +@c Fix this. +Unlike @command{diff}, @command{cmp} cannot compare directories; it can only +compare two files. + +@node Binary +@section Binary Files and Forcing Text Comparisons +@cindex binary file diff +@cindex text versus binary diff + +If @command{diff} thinks that either of the two files it is comparing is +binary (a non-text file), it normally treats that pair of files much as +if the summary output format had been selected (@pxref{Brief}), and +reports only that the binary files are different. This is because line +by line comparisons are usually not meaningful for binary files. + +@command{diff} determines whether a file is text or binary by checking the +first few bytes in the file; the exact number of bytes is system +dependent, but it is typically several thousand. If every byte in +that part of the file is non-null, @command{diff} considers the file to be +text; otherwise it considers the file to be binary. + +Sometimes you might want to force @command{diff} to consider files to be +text. For example, you might be comparing text files that contain +null characters; @command{diff} would erroneously decide that those are +non-text files. Or you might be comparing documents that are in a +format used by a word processing system that uses null characters to +indicate special formatting. You can force @command{diff} to consider all +files to be text files, and compare them line by line, by using the +@option{-a} or @option{--text} option. If the files you compare using this +option do not in fact contain text, they will probably contain few +newline characters, and the @command{diff} output will consist of hunks +showing differences between long lines of whatever characters the files +contain. + +You can also force @command{diff} to consider all files to be binary files, +and report only whether they differ (but not how). Use the +@option{-q} or @option{--brief} option for this. + +Differing binary files are considered to cause trouble because the +resulting @command{diff} output does not capture all the differences. +This trouble causes @command{diff} to exit with status 2. However, +this trouble cannot occur with the @option{--a} or @option{--text} +option, or with the @option{-q} or @option{--brief} option, as these +options both cause @command{diff} to treat binary files like text +files. + +In operating systems that distinguish between text and binary files, +@command{diff} normally reads and writes all data as text. Use the +@option{--binary} option to force @command{diff} to read and write binary +data instead. This option has no effect on a @sc{posix}-compliant system +like @sc{gnu} or traditional Unix. However, many personal computer +operating systems represent the end of a line with a carriage return +followed by a newline. On such systems, @command{diff} normally ignores +these carriage returns on input and generates them at the end of each +output line, but with the @option{--binary} option @command{diff} treats +each carriage return as just another input character, and does not +generate a carriage return at the end of each output line. This can be +useful when dealing with non-text files that are meant to be +interchanged with @sc{posix}-compliant systems. + +The @option{--strip-trailing-cr} causes @command{diff} to treat input +lines that end in carriage return followed by newline as if they end +in plain newline. This can be useful when comparing text that is +imperfectly imported from many personal computer operating systems. +This option affects how lines are read, which in turn affects how they +are compared and output. + +If you want to compare two files byte by byte, you can use the +@command{cmp} program with the @option{-l} option to show the values +of each differing byte in the two files. With @sc{gnu} @command{cmp}, +you can also use the @option{-b} option to show the @sc{ascii} +representation of those bytes. @xref{Invoking cmp}, for more +information. + +If @command{diff3} thinks that any of the files it is comparing is binary +(a non-text file), it normally reports an error, because such +comparisons are usually not useful. @command{diff3} uses the same test as +@command{diff} to decide whether a file is binary. As with @command{diff}, if +the input files contain a few non-text bytes but otherwise are like +text files, you can force @command{diff3} to consider all files to be text +files and compare them line by line by using the @option{-a} or +@option{--text} options. + +@node Output Formats +@chapter @command{diff} Output Formats +@cindex output formats +@cindex format of @command{diff} output + +@command{diff} has several mutually exclusive options for output format. +The following sections describe each format, illustrating how +@command{diff} reports the differences between two sample input files. + +@menu +* Sample diff Input:: Sample @command{diff} input files for examples. +* Normal:: Showing differences without surrounding text. +* Context:: Showing differences with the surrounding text. +* Side by Side:: Showing differences in two columns. +* Scripts:: Generating scripts for other programs. +* If-then-else:: Merging files with if-then-else. +@end menu + +@node Sample diff Input +@section Two Sample Input Files +@cindex @command{diff} sample input +@cindex sample input for @command{diff} + +Here are two sample files that we will use in numerous examples to +illustrate the output of @command{diff} and how various options can change +it. + +This is the file @file{lao}: + +@example +The Way that can be told of is not the eternal Way; +The name that can be named is not the eternal name. +The Nameless is the origin of Heaven and Earth; +The Named is the mother of all things. +Therefore let there always be non-being, + so we may see their subtlety, +And let there always be being, + so we may see their outcome. +The two are the same, +But after they are produced, + they have different names. +@end example + +This is the file @file{tzu}: + +@example +The Nameless is the origin of Heaven and Earth; +The named is the mother of all things. + +Therefore let there always be non-being, + so we may see their subtlety, +And let there always be being, + so we may see their outcome. +The two are the same, +But after they are produced, + they have different names. +They both may be called deep and profound. +Deeper and more profound, +The door of all subtleties! +@end example + +In this example, the first hunk contains just the first two lines of +@file{lao}, the second hunk contains the fourth line of @file{lao} +opposing the second and third lines of @file{tzu}, and the last hunk +contains just the last three lines of @file{tzu}. + +@node Normal +@section Showing Differences Without Context +@cindex normal output format +@cindex @samp{<} output format + +The ``normal'' @command{diff} output format shows each hunk of differences +without any surrounding context. Sometimes such output is the clearest +way to see how lines have changed, without the clutter of nearby +unchanged lines (although you can get similar results with the context +or unified formats by using 0 lines of context). However, this format +is no longer widely used for sending out patches; for that purpose, the +context format (@pxref{Context Format}) and the unified format +(@pxref{Unified Format}) are superior. Normal format is the default for +compatibility with older versions of @command{diff} and the @sc{posix} +standard. Use the @option{--normal} option to select this output +format explicitly. + +@menu +* Detailed Normal:: A detailed description of normal output format. +* Example Normal:: Sample output in the normal format. +@end menu + +@node Detailed Normal +@subsection Detailed Description of Normal Format + +The normal output format consists of one or more hunks of differences; +each hunk shows one area where the files differ. Normal format hunks +look like this: + +@example +@var{change-command} +< @var{from-file-line} +< @var{from-file-line}@dots{} +--- +> @var{to-file-line} +> @var{to-file-line}@dots{} +@end example + +There are three types of change commands. Each consists of a line +number or comma-separated range of lines in the first file, a single +character indicating the kind of change to make, and a line number or +comma-separated range of lines in the second file. All line numbers are +the original line numbers in each file. The types of change commands +are: + +@table @samp +@item @var{l}a@var{r} +Add the lines in range @var{r} of the second file after line @var{l} of +the first file. For example, @samp{8a12,15} means append lines 12--15 +of file 2 after line 8 of file 1; or, if changing file 2 into file 1, +delete lines 12--15 of file 2. + +@item @var{f}c@var{t} +Replace the lines in range @var{f} of the first file with lines in range +@var{t} of the second file. This is like a combined add and delete, but +more compact. For example, @samp{5,7c8,10} means change lines 5--7 of +file 1 to read as lines 8--10 of file 2; or, if changing file 2 into +file 1, change lines 8--10 of file 2 to read as lines 5--7 of file 1. + +@item @var{r}d@var{l} +Delete the lines in range @var{r} from the first file; line @var{l} is where +they would have appeared in the second file had they not been deleted. +For example, @samp{5,7d3} means delete lines 5--7 of file 1; or, if +changing file 2 into file 1, append lines 5--7 of file 1 after line 3 of +file 2. +@end table + +@node Example Normal +@subsection An Example of Normal Format + +Here is the output of the command @samp{diff lao tzu} +(@pxref{Sample diff Input}, for the complete contents of the two files). +Notice that it shows only the lines that are different between the two +files. + +@example +1,2d0 +< The Way that can be told of is not the eternal Way; +< The name that can be named is not the eternal name. +4c2,3 +< The Named is the mother of all things. +--- +> The named is the mother of all things. +> +11a11,13 +> They both may be called deep and profound. +> Deeper and more profound, +> The door of all subtleties! +@end example + +@node Context +@section Showing Differences in Their Context +@cindex context output format +@cindex @samp{!} output format + +Usually, when you are looking at the differences between files, you will +also want to see the parts of the files near the lines that differ, to +help you understand exactly what has changed. These nearby parts of the +files are called the @dfn{context}. + +@sc{gnu} @command{diff} provides two output formats that show context +around the differing lines: @dfn{context format} and @dfn{unified +format}. It can optionally show in which function or section of the +file the differing lines are found. + +If you are distributing new versions of files to other people in the +form of @command{diff} output, you should use one of the output formats +that show context so that they can apply the diffs even if they have +made small changes of their own to the files. @command{patch} can apply +the diffs in this case by searching in the files for the lines of +context around the differing lines; if those lines are actually a few +lines away from where the diff says they are, @command{patch} can adjust +the line numbers accordingly and still apply the diff correctly. +@xref{Imperfect}, for more information on using @command{patch} to apply +imperfect diffs. + +@menu +* Context Format:: An output format that shows surrounding lines. +* Unified Format:: A more compact output format that shows context. +* Sections:: Showing which sections of the files differences are in. +* Alternate Names:: Showing alternate file names in context headers. +@end menu + +@node Context Format +@subsection Context Format + +The context output format shows several lines of context around the +lines that differ. It is the standard format for distributing updates +to source code. + +To select this output format, use the @option{-C @var{lines}}, +@option{--context@r{[}=@var{lines}@r{]}}, or @option{-c} option. The +argument @var{lines} that some of these options take is the number of +lines of context to show. If you do not specify @var{lines}, it +defaults to three. For proper operation, @command{patch} typically needs +at least two lines of context. + +@menu +* Detailed Context:: A detailed description of the context output format. +* Example Context:: Sample output in context format. +* Less Context:: Another sample with less context. +@end menu + +@node Detailed Context +@subsubsection Detailed Description of Context Format + +The context output format starts with a two-line header, which looks +like this: + +@example +*** @var{from-file} @var{from-file-modification-time} +--- @var{to-file} @var{to-file-modification time} +@end example + +@noindent +@vindex LC_TIME +@cindex time stamp format, context diffs +The time stamp normally looks like @samp{2002-02-21 23:30:39.942229878 +-0800} to indicate the date, time with fractional seconds, and time +zone in @uref{ftp://ftp.isi.edu/in-notes/rfc2822.txt, Internet RFC +2822 format}. However, a traditional time stamp like @samp{Thu Feb 21 +23:30:39 2002} is used if the @env{LC_TIME} locale category is either +@samp{C} or @samp{POSIX}. + +You can change the header's content with the +@option{--label=@var{label}} option; see @ref{Alternate Names}. + +Next come one or more hunks of differences; each hunk shows one area +where the files differ. Context format hunks look like this: + +@example +*************** +*** @var{from-file-line-range} **** + @var{from-file-line} + @var{from-file-line}@dots{} +--- @var{to-file-line-range} ---- + @var{to-file-line} + @var{to-file-line}@dots{} +@end example + +The lines of context around the lines that differ start with two space +characters. The lines that differ between the two files start with one +of the following indicator characters, followed by a space character: + +@table @samp +@item ! +A line that is part of a group of one or more lines that changed between +the two files. There is a corresponding group of lines marked with +@samp{!} in the part of this hunk for the other file. + +@item + +An ``inserted'' line in the second file that corresponds to nothing in +the first file. + +@item - +A ``deleted'' line in the first file that corresponds to nothing in the +second file. +@end table + +If all of the changes in a hunk are insertions, the lines of +@var{from-file} are omitted. If all of the changes are deletions, the +lines of @var{to-file} are omitted. + +@node Example Context +@subsubsection An Example of Context Format + +Here is the output of @samp{diff -c lao tzu} (@pxref{Sample diff Input}, +for the complete contents of the two files). Notice that up to three +lines that are not different are shown around each line that is +different; they are the context lines. Also notice that the first two +hunks have run together, because their contents overlap. + +@example +*** lao 2002-02-21 23:30:39.942229878 -0800 +--- tzu 2002-02-21 23:30:50.442260588 -0800 +*************** +*** 1,7 **** +- The Way that can be told of is not the eternal Way; +- The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; +! The Named is the mother of all things. + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, +--- 1,6 ---- + The Nameless is the origin of Heaven and Earth; +! The named is the mother of all things. +! + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, +*************** +*** 9,11 **** +--- 8,13 ---- + The two are the same, + But after they are produced, + they have different names. ++ They both may be called deep and profound. ++ Deeper and more profound, ++ The door of all subtleties! +@end example + +@node Less Context +@subsubsection An Example of Context Format with Less Context + +Here is the output of @samp{diff -C 1 lao tzu} (@pxref{Sample diff +Input}, for the complete contents of the two files). Notice that at +most one context line is reported here. + +@example +*** lao 2002-02-21 23:30:39.942229878 -0800 +--- tzu 2002-02-21 23:30:50.442260588 -0800 +*************** +*** 1,5 **** +- The Way that can be told of is not the eternal Way; +- The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; +! The Named is the mother of all things. + Therefore let there always be non-being, +--- 1,4 ---- + The Nameless is the origin of Heaven and Earth; +! The named is the mother of all things. +! + Therefore let there always be non-being, +*************** +*** 11 **** +--- 10,13 ---- + they have different names. ++ They both may be called deep and profound. ++ Deeper and more profound, ++ The door of all subtleties! +@end example + +@node Unified Format +@subsection Unified Format +@cindex unified output format +@cindex @samp{+-} output format + +The unified output format is a variation on the context format that is +more compact because it omits redundant context lines. To select this +output format, use the @option{-U @var{lines}}, +@option{--unified@r{[}=@var{lines}@r{]}}, or @option{-u} +option. The argument @var{lines} is the number of lines of context to +show. When it is not given, it defaults to three. + +At present, only @sc{gnu} @command{diff} can produce this format and +only @sc{gnu} @command{patch} can automatically apply diffs in this +format. For proper operation, @command{patch} typically needs at +least three lines of context. + +@menu +* Detailed Unified:: A detailed description of unified format. +* Example Unified:: Sample output in unified format. +@end menu + +@node Detailed Unified +@subsubsection Detailed Description of Unified Format + +The unified output format starts with a two-line header, which looks +like this: + +@example +--- @var{from-file} @var{from-file-modification-time} ++++ @var{to-file} @var{to-file-modification-time} +@end example + +@noindent +@cindex time stamp format, unified diffs +The time stamp looks like @samp{2002-02-21 23:30:39.942229878 -0800} +to indicate the date, time with fractional seconds, and time zone. + +You can change the header's content with the +@option{--label=@var{label}} option; see @xref{Alternate Names}. + +Next come one or more hunks of differences; each hunk shows one area +where the files differ. Unified format hunks look like this: + +@example +@@@@ @var{from-file-range} @var{to-file-range} @@@@ + @var{line-from-either-file} + @var{line-from-either-file}@dots{} +@end example + +The lines common to both files begin with a space character. The lines +that actually differ between the two files have one of the following +indicator characters in the left print column: + +@table @samp +@item + +A line was added here to the first file. + +@item - +A line was removed here from the first file. +@end table + +@node Example Unified +@subsubsection An Example of Unified Format + +Here is the output of the command @samp{diff -u lao tzu} +(@pxref{Sample diff Input}, for the complete contents of the two files): + +@example +--- lao 2002-02-21 23:30:39.942229878 -0800 ++++ tzu 2002-02-21 23:30:50.442260588 -0800 +@@@@ -1,7 +1,6 @@@@ +-The Way that can be told of is not the eternal Way; +-The name that can be named is not the eternal name. + The Nameless is the origin of Heaven and Earth; +-The Named is the mother of all things. ++The named is the mother of all things. ++ + Therefore let there always be non-being, + so we may see their subtlety, + And let there always be being, +@@@@ -9,3 +8,6 @@@@ + The two are the same, + But after they are produced, + they have different names. ++They both may be called deep and profound. ++Deeper and more profound, ++The door of all subtleties! +@end example + +@node Sections +@subsection Showing Which Sections Differences Are in +@cindex headings +@cindex section headings + +Sometimes you might want to know which part of the files each change +falls in. If the files are source code, this could mean which function +was changed. If the files are documents, it could mean which chapter or +appendix was changed. @sc{gnu} @command{diff} can show this by displaying the +nearest section heading line that precedes the differing lines. Which +lines are ``section headings'' is determined by a regular expression. + +@menu +* Specified Headings:: Showing headings that match regular expressions. +* C Function Headings:: Showing headings of C functions. +@end menu + +@node Specified Headings +@subsubsection Showing Lines That Match Regular Expressions +@cindex specified headings +@cindex regular expression matching headings + +To show in which sections differences occur for files that are not +source code for C or similar languages, use the @option{-F @var{regexp}} +or @option{--show-function-line=@var{regexp}} option. @command{diff} +considers lines that match the @command{grep}-style regular expression +@var{regexp} to be the beginning +of a section of the file. Here are suggested regular expressions for +some common languages: + +@c Please add to this list, e.g. Fortran, Pascal, Perl, Python. +@table @samp +@item ^[[:alpha:]$_] +C, C++, Prolog +@item ^( +Lisp +@item ^@@node +Texinfo +@end table + +This option does not automatically select an output format; in order to +use it, you must select the context format (@pxref{Context Format}) or +unified format (@pxref{Unified Format}). In other output formats it +has no effect. + +The @option{-F} and @option{--show-function-line} options find the nearest +unchanged line that precedes each hunk of differences and matches the +given regular expression. Then they add that line to the end of the +line of asterisks in the context format, or to the @samp{@@@@} line in +unified format. If no matching line exists, they leave the output for +that hunk unchanged. If that line is more than 40 characters long, they +output only the first 40 characters. You can specify more than one +regular expression for such lines; @command{diff} tries to match each line +against each regular expression, starting with the last one given. This +means that you can use @option{-p} and @option{-F} together, if you wish. + +@node C Function Headings +@subsubsection Showing C Function Headings +@cindex C function headings +@cindex function headings, C + +To show in which functions differences occur for C and similar +languages, you can use the @option{-p} or @option{--show-c-function} option. +This option automatically defaults to the context output format +(@pxref{Context Format}), with the default number of lines of context. +You can override that number with @option{-C @var{lines}} elsewhere in the +command line. You can override both the format and the number with +@option{-U @var{lines}} elsewhere in the command line. + +The @option{-p} and @option{--show-c-function} options are equivalent to +@option{-F '^[[:alpha:]$_]'} if the unified format is specified, otherwise +@option{-c -F '^[[:alpha:]$_]'} (@pxref{Specified Headings}). @sc{gnu} +@command{diff} provides them for the sake of convenience. + +@node Alternate Names +@subsection Showing Alternate File Names +@cindex alternate file names +@cindex file name alternates + +If you are comparing two files that have meaningless or uninformative +names, you might want @command{diff} to show alternate names in the header +of the context and unified output formats. To do this, use the +@option{--label=@var{label}} option. The first time +you give this option, its argument replaces the name and date of the +first file in the header; the second time, its argument replaces the +name and date of the second file. If you give this option more than +twice, @command{diff} reports an error. The @option{--label} option does not +affect the file names in the @command{pr} header when the @option{-l} or +@option{--paginate} option is used (@pxref{Pagination}). + +Here are the first two lines of the output from @samp{diff -C 2 +--label=original --label=modified lao tzu}: + +@example +*** original +--- modified +@end example + +@node Side by Side +@section Showing Differences Side by Side +@cindex side by side +@cindex two-column output +@cindex columnar output + +@command{diff} can produce a side by side difference listing of two files. +The files are listed in two columns with a gutter between them. The +gutter contains one of the following markers: + +@table @asis +@item white space +The corresponding lines are in common. That is, either the lines are +identical, or the difference is ignored because of one of the +@option{--ignore} options (@pxref{White Space}). + +@item @samp{|} +The corresponding lines differ, and they are either both complete +or both incomplete. + +@item @samp{<} +The files differ and only the first file contains the line. + +@item @samp{>} +The files differ and only the second file contains the line. + +@item @samp{(} +Only the first file contains the line, but the difference is ignored. + +@item @samp{)} +Only the second file contains the line, but the difference is ignored. + +@item @samp{\} +The corresponding lines differ, and only the first line is incomplete. + +@item @samp{/} +The corresponding lines differ, and only the second line is incomplete. +@end table + +Normally, an output line is incomplete if and only if the lines that it +contains are incomplete; @xref{Incomplete Lines}. However, when an +output line represents two differing lines, one might be incomplete +while the other is not. In this case, the output line is complete, +but its the gutter is marked @samp{\} if the first line is incomplete, +@samp{/} if the second line is. + +Side by side format is sometimes easiest to read, but it has limitations. +It generates much wider output than usual, and truncates lines that are +too long to fit. Also, it relies on lining up output more heavily than +usual, so its output looks particularly bad if you use varying +width fonts, nonstandard tab stops, or nonprinting characters. + +You can use the @command{sdiff} command to interactively merge side by side +differences. @xref{Interactive Merging}, for more information on merging files. + +@menu +* Side by Side Format:: Controlling side by side output format. +* Example Side by Side:: Sample side by side output. +@end menu + +@node Side by Side Format +@subsection Controlling Side by Side Format +@cindex side by side format + +The @option{-y} or @option{--side-by-side} option selects side by side +format. Because side by side output lines contain two input lines, the +output is wider than usual: normally 130 print columns, which can fit +onto a traditional printer line. You can set the width of the output +with the @option{-W @var{columns}} or @option{--width=@var{columns}} +option. The output is split into two halves of equal width, separated by a +small gutter to mark differences; the right half is aligned to a tab +stop so that tabs line up. Input lines that are too long to fit in half +of an output line are truncated for output. + +The @option{--left-column} option prints only the left column of two +common lines. The @option{--suppress-common-lines} option suppresses +common lines entirely. + +@node Example Side by Side +@subsection An Example of Side by Side Format + +Here is the output of the command @samp{diff -y -W 72 lao tzu} +(@pxref{Sample diff Input}, for the complete contents of the two files). + +@example +The Way that can be told of is n < +The name that can be named is no < +The Nameless is the origin of He The Nameless is the origin of He +The Named is the mother of all t | The named is the mother of all t + > +Therefore let there always be no Therefore let there always be no + so we may see their subtlety, so we may see their subtlety, +And let there always be being, And let there always be being, + so we may see their outcome. so we may see their outcome. +The two are the same, The two are the same, +But after they are produced, But after they are produced, + they have different names. they have different names. + > They both may be called deep and + > Deeper and more profound, + > The door of all subtleties! +@end example + +@node Scripts +@section Making Edit Scripts +@cindex script output formats + +Several output modes produce command scripts for editing @var{from-file} +to produce @var{to-file}. + +@menu +* ed Scripts:: Using @command{diff} to produce commands for @command{ed}. +* Forward ed:: Making forward @command{ed} scripts. +* RCS:: A special @command{diff} output format used by @sc{rcs}. +@end menu + +@node ed Scripts +@subsection @command{ed} Scripts +@cindex @command{ed} script output format + +@command{diff} can produce commands that direct the @command{ed} text editor +to change the first file into the second file. Long ago, this was the +only output mode that was suitable for editing one file into another +automatically; today, with @command{patch}, it is almost obsolete. Use the +@option{-e} or @option{--ed} option to select this output format. + +Like the normal format (@pxref{Normal}), this output format does not +show any context; unlike the normal format, it does not include the +information necessary to apply the diff in reverse (to produce the first +file if all you have is the second file and the diff). + +If the file @file{d} contains the output of @samp{diff -e old new}, then +the command @samp{(cat d && echo w) | ed - old} edits @file{old} to make +it a copy of @file{new}. More generally, if @file{d1}, @file{d2}, +@dots{}, @file{dN} contain the outputs of @samp{diff -e old new1}, +@samp{diff -e new1 new2}, @dots{}, @samp{diff -e newN-1 newN}, +respectively, then the command @samp{(cat d1 d2 @dots{} dN && echo w) | +ed - old} edits @file{old} to make it a copy of @file{newN}. + +@menu +* Detailed ed:: A detailed description of @command{ed} format. +* Example ed:: A sample @command{ed} script. +@end menu + +@node Detailed ed +@subsubsection Detailed Description of @command{ed} Format + +The @command{ed} output format consists of one or more hunks of +differences. The changes closest to the ends of the files come first so +that commands that change the number of lines do not affect how +@command{ed} interprets line numbers in succeeding commands. @command{ed} +format hunks look like this: + +@example +@var{change-command} +@var{to-file-line} +@var{to-file-line}@dots{} +. +@end example + +Because @command{ed} uses a single period on a line to indicate the end of +input, @sc{gnu} @command{diff} protects lines of changes that contain a single +period on a line by writing two periods instead, then writing a +subsequent @command{ed} command to change the two periods into one. The +@command{ed} format cannot represent an incomplete line, so if the second +file ends in a changed incomplete line, @command{diff} reports an error and +then pretends that a newline was appended. + +There are three types of change commands. Each consists of a line +number or comma-separated range of lines in the first file and a single +character indicating the kind of change to make. All line numbers are +the original line numbers in the file. The types of change commands +are: + +@table @samp +@item @var{l}a +Add text from the second file after line @var{l} in the first file. For +example, @samp{8a} means to add the following lines after line 8 of file +1. + +@item @var{r}c +Replace the lines in range @var{r} in the first file with the following +lines. Like a combined add and delete, but more compact. For example, +@samp{5,7c} means change lines 5--7 of file 1 to read as the text file +2. + +@item @var{r}d +Delete the lines in range @var{r} from the first file. For example, +@samp{5,7d} means delete lines 5--7 of file 1. +@end table + +@node Example ed +@subsubsection Example @command{ed} Script + +Here is the output of @samp{diff -e lao tzu} (@pxref{Sample +diff Input}, for the complete contents of the two files): + +@example +11a +They both may be called deep and profound. +Deeper and more profound, +The door of all subtleties! +. +4c +The named is the mother of all things. + +. +1,2d +@end example + +@node Forward ed +@subsection Forward @command{ed} Scripts +@cindex forward @command{ed} script output format + +@command{diff} can produce output that is like an @command{ed} script, but +with hunks in forward (front to back) order. The format of the commands +is also changed slightly: command characters precede the lines they +modify, spaces separate line numbers in ranges, and no attempt is made +to disambiguate hunk lines consisting of a single period. Like +@command{ed} format, forward @command{ed} format cannot represent incomplete +lines. + +Forward @command{ed} format is not very useful, because neither @command{ed} +nor @command{patch} can apply diffs in this format. It exists mainly for +compatibility with older versions of @command{diff}. Use the @option{-f} or +@option{--forward-ed} option to select it. + +@node RCS +@subsection @sc{rcs} Scripts +@cindex @sc{rcs} script output format + +The @sc{rcs} output format is designed specifically for use by the Revision +Control System, which is a set of free programs used for organizing +different versions and systems of files. Use the @option{-n} or +@option{--rcs} option to select this output format. It is like the +forward @command{ed} format (@pxref{Forward ed}), but it can represent +arbitrary changes to the contents of a file because it avoids the +forward @command{ed} format's problems with lines consisting of a single +period and with incomplete lines. Instead of ending text sections with +a line consisting of a single period, each command specifies the number +of lines it affects; a combination of the @samp{a} and @samp{d} +commands are used instead of @samp{c}. Also, if the second file ends +in a changed incomplete line, then the output also ends in an +incomplete line. + +Here is the output of @samp{diff -n lao tzu} (@pxref{Sample +diff Input}, for the complete contents of the two files): + +@example +d1 2 +d4 1 +a4 2 +The named is the mother of all things. + +a11 3 +They both may be called deep and profound. +Deeper and more profound, +The door of all subtleties! +@end example + +@node If-then-else +@section Merging Files with If-then-else +@cindex merged output format +@cindex if-then-else output format +@cindex C if-then-else output format +@cindex @command{ifdef} output format + +You can use @command{diff} to merge two files of C source code. The output +of @command{diff} in this format contains all the lines of both files. +Lines common to both files are output just once; the differing parts are +separated by the C preprocessor directives @code{#ifdef @var{name}} or +@code{#ifndef @var{name}}, @code{#else}, and @code{#endif}. When +compiling the output, you select which version to use by either defining +or leaving undefined the macro @var{name}. + +To merge two files, use @command{diff} with the @option{-D @var{name}} or +@option{--ifdef=@var{name}} option. The argument @var{name} is the C +preprocessor identifier to use in the @code{#ifdef} and @code{#ifndef} +directives. + +For example, if you change an instance of @code{wait (&s)} to +@code{waitpid (-1, &s, 0)} and then merge the old and new files with +the @option{--ifdef=HAVE_WAITPID} option, then the affected part of your code +might look like this: + +@example + do @{ +#ifndef HAVE_WAITPID + if ((w = wait (&s)) < 0 && errno != EINTR) +#else /* HAVE_WAITPID */ + if ((w = waitpid (-1, &s, 0)) < 0 && errno != EINTR) +#endif /* HAVE_WAITPID */ + return w; + @} while (w != child); +@end example + +You can specify formats for languages other than C by using line group +formats and line formats, as described in the next sections. + +@menu +* Line Group Formats:: Formats for general if-then-else line groups. +* Line Formats:: Formats for each line in a line group. +* Detailed If-then-else:: A detailed description of if-then-else format. +* Example If-then-else:: Sample if-then-else format output. +@end menu + +@node Line Group Formats +@subsection Line Group Formats +@cindex line group formats +@cindex formats for if-then-else line groups + +Line group formats let you specify formats suitable for many +applications that allow if-then-else input, including programming +languages and text formatting languages. A line group format specifies +the output format for a contiguous group of similar lines. + +For example, the following command compares the TeX files @file{old} +and @file{new}, and outputs a merged file in which old regions are +surrounded by @samp{\begin@{em@}}-@samp{\end@{em@}} lines, and new +regions are surrounded by @samp{\begin@{bf@}}-@samp{\end@{bf@}} lines. + +@example +diff \ + --old-group-format='\begin@{em@} +%<\end@{em@} +' \ + --new-group-format='\begin@{bf@} +%>\end@{bf@} +' \ + old new +@end example + +The following command is equivalent to the above example, but it is a +little more verbose, because it spells out the default line group formats. + +@example +diff \ + --old-group-format='\begin@{em@} +%<\end@{em@} +' \ + --new-group-format='\begin@{bf@} +%>\end@{bf@} +' \ + --unchanged-group-format='%=' \ + --changed-group-format='\begin@{em@} +%<\end@{em@} +\begin@{bf@} +%>\end@{bf@} +' \ + old new +@end example + +Here is a more advanced example, which outputs a diff listing with +headers containing line numbers in a ``plain English'' style. + +@example +diff \ + --unchanged-group-format='' \ + --old-group-format='-------- %dn line%(n=1?:s) deleted at %df: +%<' \ + --new-group-format='-------- %dN line%(N=1?:s) added after %de: +%>' \ + --changed-group-format='-------- %dn line%(n=1?:s) changed at %df: +%<-------- to: +%>' \ + old new +@end example + +To specify a line group format, use @command{diff} with one of the options +listed below. You can specify up to four line group formats, one for +each kind of line group. You should quote @var{format}, because it +typically contains shell metacharacters. + +@table @option +@item --old-group-format=@var{format} +These line groups are hunks containing only lines from the first file. +The default old group format is the same as the changed group format if +it is specified; otherwise it is a format that outputs the line group as-is. + +@item --new-group-format=@var{format} +These line groups are hunks containing only lines from the second +file. The default new group format is same as the changed group +format if it is specified; otherwise it is a format that outputs the +line group as-is. + +@item --changed-group-format=@var{format} +These line groups are hunks containing lines from both files. The +default changed group format is the concatenation of the old and new +group formats. + +@item --unchanged-group-format=@var{format} +These line groups contain lines common to both files. The default +unchanged group format is a format that outputs the line group as-is. +@end table + +In a line group format, ordinary characters represent themselves; +conversion specifications start with @samp{%} and have one of the +following forms. + +@table @samp +@item %< +stands for the lines from the first file, including the trailing newline. +Each line is formatted according to the old line format (@pxref{Line Formats}). + +@item %> +stands for the lines from the second file, including the trailing newline. +Each line is formatted according to the new line format. + +@item %= +stands for the lines common to both files, including the trailing newline. +Each line is formatted according to the unchanged line format. + +@item %% +stands for @samp{%}. + +@item %c'@var{C}' +where @var{C} is a single character, stands for @var{C}. +@var{C} may not be a backslash or an apostrophe. +For example, @samp{%c':'} stands for a colon, even inside +the then-part of an if-then-else format, which a colon would +normally terminate. + +@item %c'\@var{O}' +where @var{O} is a string of 1, 2, or 3 octal digits, +stands for the character with octal code @var{O}. +For example, @samp{%c'\0'} stands for a null character. + +@item @var{F}@var{n} +where @var{F} is a @code{printf} conversion specification and @var{n} is one +of the following letters, stands for @var{n}'s value formatted with @var{F}. + +@table @samp +@item e +The line number of the line just before the group in the old file. + +@item f +The line number of the first line in the group in the old file; +equals @var{e} + 1. + +@item l +The line number of the last line in the group in the old file. + +@item m +The line number of the line just after the group in the old file; +equals @var{l} + 1. + +@item n +The number of lines in the group in the old file; equals @var{l} - @var{f} + 1. + +@item E, F, L, M, N +Likewise, for lines in the new file. + +@end table + +@vindex LC_NUMERIC +The @code{printf} conversion specification can be @samp{%d}, +@samp{%o}, @samp{%x}, or @samp{%X}, specifying decimal, octal, +lower case hexadecimal, or upper case hexadecimal output +respectively. After the @samp{%} the following options can appear in +sequence: a series of zero or more flags; an integer +specifying the minimum field width; and a period followed by an +optional integer specifying the minimum number of digits. +The flags are @samp{-} for left-justification, @samp{'} for separating +the digit into groups as specified by the @env{LC_NUMERIC} locale category, +and @samp{0} for padding with zeros instead of spaces. +For example, @samp{%5dN} prints the number of new lines in the group +in a field of width 5 characters, using the @code{printf} format @code{"%5d"}. + +@item (@var{A}=@var{B}?@var{T}:@var{E}) +If @var{A} equals @var{B} then @var{T} else @var{E}. +@var{A} and @var{B} are each either a decimal constant +or a single letter interpreted as above. +This format spec is equivalent to @var{T} if +@var{A}'s value equals @var{B}'s; otherwise it is equivalent to @var{E}. + +For example, @samp{%(N=0?no:%dN) line%(N=1?:s)} is equivalent to +@samp{no lines} if @var{N} (the number of lines in the group in the the +new file) is 0, to @samp{1 line} if @var{N} is 1, and to @samp{%dN lines} +otherwise. +@end table + +@node Line Formats +@subsection Line Formats +@cindex line formats + +Line formats control how each line taken from an input file is +output as part of a line group in if-then-else format. + +For example, the following command outputs text with a one-character +change indicator to the left of the text. The first character of output +is @samp{-} for deleted lines, @samp{|} for added lines, and a space for +unchanged lines. The formats contain newline characters where newlines +are desired on output. + +@example +diff \ + --old-line-format='-%l +' \ + --new-line-format='|%l +' \ + --unchanged-line-format=' %l +' \ + old new +@end example + +To specify a line format, use one of the following options. You should +quote @var{format}, since it often contains shell metacharacters. + +@table @option +@item --old-line-format=@var{format} +formats lines just from the first file. + +@item --new-line-format=@var{format} +formats lines just from the second file. + +@item --unchanged-line-format=@var{format} +formats lines common to both files. + +@item --line-format=@var{format} +formats all lines; in effect, it sets all three above options simultaneously. +@end table + +In a line format, ordinary characters represent themselves; +conversion specifications start with @samp{%} and have one of the +following forms. + +@table @samp +@item %l +stands for the contents of the line, not counting its trailing +newline (if any). This format ignores whether the line is incomplete; +@xref{Incomplete Lines}. + +@item %L +stands for the contents of the line, including its trailing newline +(if any). If a line is incomplete, this format preserves its +incompleteness. + +@item %% +stands for @samp{%}. + +@item %c'@var{C}' +where @var{C} is a single character, stands for @var{C}. +@var{C} may not be a backslash or an apostrophe. +For example, @samp{%c':'} stands for a colon. + +@item %c'\@var{O}' +where @var{O} is a string of 1, 2, or 3 octal digits, +stands for the character with octal code @var{O}. +For example, @samp{%c'\0'} stands for a null character. + +@item @var{F}n +where @var{F} is a @code{printf} conversion specification, +stands for the line number formatted with @var{F}. +For example, @samp{%.5dn} prints the line number using the +@code{printf} format @code{"%.5d"}. @xref{Line Group Formats}, for +more about printf conversion specifications. + +@end table + +The default line format is @samp{%l} followed by a newline character. + +If the input contains tab characters and it is important that they line +up on output, you should ensure that @samp{%l} or @samp{%L} in a line +format is just after a tab stop (e.g.@: by preceding @samp{%l} or +@samp{%L} with a tab character), or you should use the @option{-t} or +@option{--expand-tabs} option. + +Taken together, the line and line group formats let you specify many +different formats. For example, the following command uses a format +similar to normal @command{diff} format. You can tailor this command +to get fine control over @command{diff} output. + +@example +diff \ + --old-line-format='< %l +' \ + --new-line-format='> %l +' \ + --old-group-format='%df%(f=l?:,%dl)d%dE +%<' \ + --new-group-format='%dea%dF%(F=L?:,%dL) +%>' \ + --changed-group-format='%df%(f=l?:,%dl)c%dF%(F=L?:,%dL) +%<--- +%>' \ + --unchanged-group-format='' \ + old new +@end example + +@node Detailed If-then-else +@subsection Detailed Description of If-then-else Format + +For lines common to both files, @command{diff} uses the unchanged line +group format. For each hunk of differences in the merged output +format, if the hunk contains only lines from the first file, +@command{diff} uses the old line group format; if the hunk contains only +lines from the second file, @command{diff} uses the new group format; +otherwise, @command{diff} uses the changed group format. + +The old, new, and unchanged line formats specify the output format of +lines from the first file, lines from the second file, and lines common +to both files, respectively. + +The option @option{--ifdef=@var{name}} is equivalent to +the following sequence of options using shell syntax: + +@example +--old-group-format='#ifndef @var{name} +%<#endif /* ! @var{name} */ +' \ +--new-group-format='#ifdef @var{name} +%>#endif /* @var{name} */ +' \ +--unchanged-group-format='%=' \ +--changed-group-format='#ifndef @var{name} +%<#else /* @var{name} */ +%>#endif /* @var{name} */ +' +@end example + +You should carefully check the @command{diff} output for proper nesting. +For example, when using the @option{-D @var{name}} or +@option{--ifdef=@var{name}} option, you should check that if the +differing lines contain any of the C preprocessor directives +@samp{#ifdef}, @samp{#ifndef}, @samp{#else}, @samp{#elif}, or +@samp{#endif}, they are nested properly and match. If they don't, you +must make corrections manually. It is a good idea to carefully check +the resulting code anyway to make sure that it really does what you +want it to; depending on how the input files were produced, the output +might contain duplicate or otherwise incorrect code. + +The @command{patch} @option{-D @var{name}} option behaves like +the @command{diff} @option{-D @var{name}} option, except it operates on +a file and a diff to produce a merged file; @xref{patch Options}. + +@node Example If-then-else +@subsection An Example of If-then-else Format + +Here is the output of @samp{diff -DTWO lao tzu} (@pxref{Sample +diff Input}, for the complete contents of the two files): + +@example +#ifndef TWO +The Way that can be told of is not the eternal Way; +The name that can be named is not the eternal name. +#endif /* ! TWO */ +The Nameless is the origin of Heaven and Earth; +#ifndef TWO +The Named is the mother of all things. +#else /* TWO */ +The named is the mother of all things. + +#endif /* TWO */ +Therefore let there always be non-being, + so we may see their subtlety, +And let there always be being, + so we may see their outcome. +The two are the same, +But after they are produced, + they have different names. +#ifdef TWO +They both may be called deep and profound. +Deeper and more profound, +The door of all subtleties! +#endif /* TWO */ +@end example + +@node Incomplete Lines +@chapter Incomplete Lines +@cindex incomplete lines +@cindex full lines +@cindex newline treatment by @command{diff} + +When an input file ends in a non-newline character, its last line is +called an @dfn{incomplete line} because its last character is not a +newline. All other lines are called @dfn{full lines} and end in a +newline character. Incomplete lines do not match full lines unless +differences in white space are ignored (@pxref{White Space}). + +An incomplete line is normally distinguished on output from a full line +by a following line that starts with @samp{\}. However, the @sc{rcs} format +(@pxref{RCS}) outputs the incomplete line as-is, without any trailing +newline or following line. The side by side format normally represents +incomplete lines as-is, but in some cases uses a @samp{\} or @samp{/} +gutter marker; @xref{Side by Side}. The if-then-else line format +preserves a line's incompleteness with @samp{%L}, and discards the +newline with @samp{%l}; @xref{Line Formats}. Finally, with the +@command{ed} and forward @command{ed} output formats (@pxref{Output Formats}) +@command{diff} cannot represent an incomplete line, so it pretends there +was a newline and reports an error. + +For example, suppose @file{F} and @file{G} are one-byte files that +contain just @samp{f} and @samp{g}, respectively. Then @samp{diff F G} +outputs + +@example +1c1 +< f +\ No newline at end of file +--- +> g +\ No newline at end of file +@end example + +@noindent +(The exact message may differ in non-English locales.) +@samp{diff -n F G} outputs the following without a trailing newline: + +@example +d1 1 +a1 1 +g +@end example + +@noindent +@samp{diff -e F G} reports two errors and outputs the following: + +@example +1c +g +. +@end example + +@node Comparing Directories +@chapter Comparing Directories + +@vindex LC_COLLATE +You can use @command{diff} to compare some or all of the files in two +directory trees. When both file name arguments to @command{diff} are +directories, it compares each file that is contained in both +directories, examining file names in alphabetical order as specified by +the @env{LC_COLLATE} locale category. Normally +@command{diff} is silent about pairs of files that contain no differences, +but if you use the @option{-s} or @option{--report-identical-files} option, +it reports pairs of identical files. Normally @command{diff} reports +subdirectories common to both directories without comparing +subdirectories' files, but if you use the @option{-r} or +@option{--recursive} option, it compares every corresponding pair of files +in the directory trees, as many levels deep as they go. + +For file names that are in only one of the directories, @command{diff} +normally does not show the contents of the file that exists; it reports +only that the file exists in that directory and not in the other. You +can make @command{diff} act as though the file existed but was empty in the +other directory, so that it outputs the entire contents of the file that +actually exists. (It is output as either an insertion or a +deletion, depending on whether it is in the first or the second +directory given.) To do this, use the @option{-N} or @option{--new-file} +option. + +If the older directory contains one or more large files that are not in +the newer directory, you can make the patch smaller by using the +@option{--unidirectional-new-file} option instead of @option{-N}. +This option is like @option{-N} except that it only inserts the contents +of files that appear in the second directory but not the first (that is, +files that were added). At the top of the patch, write instructions for +the user applying the patch to remove the files that were deleted before +applying the patch. @xref{Making Patches}, for more discussion of +making patches for distribution. + +To ignore some files while comparing directories, use the @option{-x +@var{pattern}} or @option{--exclude=@var{pattern}} option. This option +ignores any files or subdirectories whose base names match the shell +pattern @var{pattern}. Unlike in the shell, a period at the start of +the base of a file name matches a wildcard at the start of a pattern. +You should enclose @var{pattern} in quotes so that the shell does not +expand it. For example, the option @option{-x '*.[ao]'} ignores any file +whose name ends with @samp{.a} or @samp{.o}. + +This option accumulates if you specify it more than once. For example, +using the options @option{-x 'RCS' -x '*,v'} ignores any file or +subdirectory whose base name is @samp{RCS} or ends with @samp{,v}. + +If you need to give this option many times, you can instead put the +patterns in a file, one pattern per line, and use the @option{-X +@var{file}} or @option{--exclude-from=@var{file}} option. + +If you have been comparing two directories and stopped partway through, +later you might want to continue where you left off. You can do this by +using the @option{-S @var{file}} or @option{--starting-file=@var{file}} +option. This compares only the file @var{file} and all alphabetically +later files in the topmost directory level. + +If two directories differ only in that file names are lower case in +one directory and upper case in the upper, @command{diff} normally +reports many differences because it compares file names in a +case sensitive way. With the @option{--ignore-file-name-case} option, +@command{diff} ignores case differences in file names, so that for example +the contents of the file @file{Tao} in one directory are compared to +the contents of the file @file{TAO} in the other. The +@option{--no-ignore-file-name-case} option cancels the effect of the +@option{--ignore-file-name-case} option, reverting to the default +behavior. + +If an @option{-x @var{pattern}}, @option{--exclude=@var{pattern}}, +@option{-X @var{file}}, or @option{--exclude-from=@var{file}} option +is specified while the @option{--ignore-file-name-case} option is in +effect, case is ignored when excluding file names matching the +specified patterns. + +@node Adjusting Output +@chapter Making @command{diff} Output Prettier + +@command{diff} provides several ways to adjust the appearance of its output. +These adjustments can be applied to any output format. + +@menu +* Tabs:: Preserving the alignment of tab stops. +* Pagination:: Page numbering and time-stamping @command{diff} output. +@end menu + +@node Tabs +@section Preserving Tab Stop Alignment +@cindex tab stop alignment +@cindex aligning tab stops + +The lines of text in some of the @command{diff} output formats are preceded +by one or two characters that indicate whether the text is inserted, +deleted, or changed. The addition of those characters can cause tabs to +move to the next tab stop, throwing off the alignment of columns in the +line. @sc{gnu} @command{diff} provides two ways to make tab-aligned columns +line up correctly. + +The first way is to have @command{diff} convert all tabs into the correct +number of spaces before outputting them; select this method with the +@option{-t} or @option{--expand-tabs} option. @command{diff} assumes that +tab stops are set every 8 print columns. To use this form of output with +@command{patch}, you must give @command{patch} the @option{-l} or +@option{--ignore-white-space} option (@pxref{Changed White Space}, for more +information). + +The other method for making tabs line up correctly is to add a tab +character instead of a space after the indicator character at the +beginning of the line. This ensures that all following tab characters +are in the same position relative to tab stops that they were in the +original files, so that the output is aligned correctly. Its +disadvantage is that it can make long lines too long to fit on one line +of the screen or the paper. It also does not work with the unified +output format, which does not have a space character after the change +type indicator character. Select this method with the @option{-T} or +@option{--initial-tab} option. + +@node Pagination +@section Paginating @command{diff} Output +@cindex paginating @command{diff} output + +It can be convenient to have long output page-numbered and time-stamped. +The @option{-l} and @option{--paginate} options do this by sending the +@command{diff} output through the @command{pr} program. Here is what the page +header might look like for @samp{diff -lc lao tzu}: + +@example +2002-02-22 14:20 diff -lc lao tzu Page 1 +@end example + +@node diff Performance +@chapter @command{diff} Performance Tradeoffs +@cindex performance of @command{diff} + +@sc{gnu} @command{diff} runs quite efficiently; however, in some circumstances +you can cause it to run faster or produce a more compact set of changes. + +One way to improve @command{diff} performance is to use hard or +symbolic links to files instead of copies. This improves performance +because @command{diff} normally does not need to read two hard or +symbolic links to the same file, since their contents must be +identical. For example, suppose you copy a large directory hierarchy, +make a few changes to the copy, and then often use @samp{diff -r} to +compare the original to the copy. If the original files are +read-only, you can greatly improve performance by creating the copy +using hard or symbolic links (e.g., with @sc{gnu} @samp{cp -lR} or +@samp{cp -sR}). Before editing a file in the copy for the first time, +you should break the link and replace it with a regular copy. + +You can also affect the performance of @sc{gnu} @command{diff} by +giving it options that change the way it compares files. +Performance has more than one dimension. These options improve one +aspect of performance at the cost of another, or they improve +performance in some cases while hurting it in others. + +The way that @sc{gnu} @command{diff} determines which lines have changed always +comes up with a near-minimal set of differences. Usually it is good +enough for practical purposes. If the @command{diff} output is large, you +might want @command{diff} to use a modified algorithm that sometimes +produces a smaller set of differences. The @option{-d} or +@option{--minimal} option does this; however, it can also cause +@command{diff} to run more slowly than usual, so it is not the default +behavior. + +When the files you are comparing are large and have small groups of +changes scattered throughout them, you can use the +@option{--speed-large-files} option to make a different modification to +the algorithm that @command{diff} uses. If the input files have a constant +small density of changes, this option speeds up the comparisons without +changing the output. If not, @command{diff} might produce a larger set of +differences; however, the output will still be correct. + +Normally @command{diff} discards the prefix and suffix that is common to +both files before it attempts to find a minimal set of differences. +This makes @command{diff} run faster, but occasionally it may produce +non-minimal output. The @option{--horizon-lines=@var{lines}} option +prevents @command{diff} from discarding the last @var{lines} lines of the +prefix and the first @var{lines} lines of the suffix. This gives +@command{diff} further opportunities to find a minimal output. + +Suppose a run of changed lines includes a sequence of lines at one end +and there is an identical sequence of lines just outside the other end. +The @command{diff} command is free to choose which identical sequence is +included in the hunk. In this case, @command{diff} normally shifts the +hunk's boundaries when this merges adjacent hunks, or shifts a hunk's +lines towards the end of the file. Merging hunks can make the output +look nicer in some cases. + +@node Comparing Three Files +@chapter Comparing Three Files +@cindex comparing three files +@cindex format of @command{diff3} output + +Use the program @command{diff3} to compare three files and show any +differences among them. (@command{diff3} can also merge files; see +@ref{diff3 Merging}). + +The ``normal'' @command{diff3} output format shows each hunk of +differences without surrounding context. Hunks are labeled depending +on whether they are two-way or three-way, and lines are annotated by +their location in the input files. + +@xref{Invoking diff3}, for more information on how to run @command{diff3}. + +@menu +* Sample diff3 Input:: Sample @command{diff3} input for examples. +* Detailed diff3 Normal:: A detailed description of normal output format. +* diff3 Hunks:: The format of normal output format. +* Example diff3 Normal:: Sample output in the normal format. +@end menu + +@node Sample diff3 Input +@section A Third Sample Input File +@cindex @command{diff3} sample input +@cindex sample input for @command{diff3} + +Here is a third sample file that will be used in examples to illustrate +the output of @command{diff3} and how various options can change it. The +first two files are the same that we used for @command{diff} (@pxref{Sample +diff Input}). This is the third sample file, called @file{tao}: + +@example +The Way that can be told of is not the eternal Way; +The name that can be named is not the eternal name. +The Nameless is the origin of Heaven and Earth; +The named is the mother of all things. + +Therefore let there always be non-being, + so we may see their subtlety, +And let there always be being, + so we may see their result. +The two are the same, +But after they are produced, + they have different names. + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan +@end example + +@node Detailed diff3 Normal +@section Detailed Description of @command{diff3} Normal Format + +Each hunk begins with a line marked @samp{====}. Three-way hunks have +plain @samp{====} lines, and two-way hunks have @samp{1}, @samp{2}, or +@samp{3} appended to specify which of the three input files differ in +that hunk. The hunks contain copies of two or three sets of input +lines each preceded by one or two commands identifying where the lines +came from. + +Normally, two spaces precede each copy of an input line to distinguish +it from the commands. But with the @option{-T} or @option{--initial-tab} +option, @command{diff3} uses a tab instead of two spaces; this lines up +tabs correctly. @xref{Tabs}, for more information. + +Commands take the following forms: + +@table @samp +@item @var{file}:@var{l}a +This hunk appears after line @var{l} of file @var{file}, and +contains no lines in that file. To edit this file to yield the other +files, one must append hunk lines taken from the other files. For +example, @samp{1:11a} means that the hunk follows line 11 in the first +file and contains no lines from that file. + +@item @var{file}:@var{r}c +This hunk contains the lines in the range @var{r} of file @var{file}. +The range @var{r} is a comma-separated pair of line numbers, or just one +number if the range is a singleton. To edit this file to yield the +other files, one must change the specified lines to be the lines taken +from the other files. For example, @samp{2:11,13c} means that the hunk +contains lines 11 through 13 from the second file. +@end table + +If the last line in a set of input lines is incomplete +(@pxref{Incomplete Lines}), it is distinguished on output from a full +line by a following line that starts with @samp{\}. + +@node diff3 Hunks +@section @command{diff3} Hunks +@cindex hunks for @command{diff3} +@cindex @command{diff3} hunks + +Groups of lines that differ in two or three of the input files are +called @dfn{diff3 hunks}, by analogy with @command{diff} hunks +(@pxref{Hunks}). If all three input files differ in a @command{diff3} +hunk, the hunk is called a @dfn{three-way hunk}; if just two input files +differ, it is a @dfn{two-way hunk}. + +As with @command{diff}, several solutions are possible. When comparing the +files @samp{A}, @samp{B}, and @samp{C}, @command{diff3} normally finds +@command{diff3} hunks by merging the two-way hunks output by the two +commands @samp{diff A B} and @samp{diff A C}. This does not necessarily +minimize the size of the output, but exceptions should be rare. + +For example, suppose @file{F} contains the three lines @samp{a}, +@samp{b}, @samp{f}, @file{G} contains the lines @samp{g}, @samp{b}, +@samp{g}, and @file{H} contains the lines @samp{a}, @samp{b}, +@samp{h}. @samp{diff3 F G H} might output the following: + +@example +====2 +1:1c +3:1c + a +2:1c + g +==== +1:3c + f +2:3c + g +3:3c + h +@end example + +@noindent +because it found a two-way hunk containing @samp{a} in the first and +third files and @samp{g} in the second file, then the single line +@samp{b} common to all three files, then a three-way hunk containing +the last line of each file. + +@node Example diff3 Normal +@section An Example of @command{diff3} Normal Format + +Here is the output of the command @samp{diff3 lao tzu tao} +(@pxref{Sample diff3 Input}, for the complete contents of the files). +Notice that it shows only the lines that are different among the three +files. + +@example +====2 +1:1,2c +3:1,2c + The Way that can be told of is not the eternal Way; + The name that can be named is not the eternal name. +2:0a +====1 +1:4c + The Named is the mother of all things. +2:2,3c +3:4,5c + The named is the mother of all things. + +====3 +1:8c +2:7c + so we may see their outcome. +3:9c + so we may see their result. +==== +1:11a +2:11,13c + They both may be called deep and profound. + Deeper and more profound, + The door of all subtleties! +3:13,14c + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan +@end example + +@node diff3 Merging +@chapter Merging From a Common Ancestor +@cindex merging from a common ancestor + +When two people have made changes to copies of the same file, +@command{diff3} can produce a merged output that contains both sets of +changes together with warnings about conflicts. + +One might imagine programs with names like @command{diff4} and @command{diff5} +to compare more than three files simultaneously, but in practice the +need rarely arises. You can use @command{diff3} to merge three or more +sets of changes to a file by merging two change sets at a time. + +@command{diff3} can incorporate changes from two modified versions into a +common preceding version. This lets you merge the sets of changes +represented by the two newer files. Specify the common ancestor version +as the second argument and the two newer versions as the first and third +arguments, like this: + +@example +diff3 @var{mine} @var{older} @var{yours} +@end example + +@noindent +You can remember the order of the arguments by noting that they are in +alphabetical order. + +@cindex conflict +@cindex overlap +You can think of this as subtracting @var{older} from @var{yours} and +adding the result to @var{mine}, or as merging into @var{mine} the +changes that would turn @var{older} into @var{yours}. This merging is +well-defined as long as @var{mine} and @var{older} match in the +neighborhood of each such change. This fails to be true when all three +input files differ or when only @var{older} differs; we call this +a @dfn{conflict}. When all three input files differ, we call the +conflict an @dfn{overlap}. + +@command{diff3} gives you several ways to handle overlaps and conflicts. +You can omit overlaps or conflicts, or select only overlaps, +or mark conflicts with special @samp{<<<<<<<} and @samp{>>>>>>>} lines. + +@command{diff3} can output the merge results as an @command{ed} script that +that can be applied to the first file to yield the merged output. +However, it is usually better to have @command{diff3} generate the merged +output directly; this bypasses some problems with @command{ed}. + +@menu +* Which Changes:: Selecting changes to incorporate. +* Marking Conflicts:: Marking conflicts. +* Bypassing ed:: Generating merged output directly. +* Merging Incomplete Lines:: How @command{diff3} merges incomplete lines. +* Saving the Changed File:: Emulating System V behavior. +@end menu + +@node Which Changes +@section Selecting Which Changes to Incorporate +@cindex overlapping change, selection of +@cindex unmerged change + +You can select all unmerged changes from @var{older} to @var{yours} for merging +into @var{mine} with the @option{-e} or @option{--ed} option. You can +select only the nonoverlapping unmerged changes with @option{-3} or +@option{--easy-only}, and you can select only the overlapping changes with +@option{-x} or @option{--overlap-only}. + +The @option{-e}, @option{-3} and @option{-x} options select only +@dfn{unmerged changes}, i.e.@: changes where @var{mine} and @var{yours} +differ; they ignore changes from @var{older} to @var{yours} where +@var{mine} and @var{yours} are identical, because they assume that such +changes have already been merged. If this assumption is not a safe +one, you can use the @option{-A} or @option{--show-all} option +(@pxref{Marking Conflicts}). + +Here is the output of the command @command{diff3} with each of these three +options (@pxref{Sample diff3 Input}, for the complete contents of the files). +Notice that @option{-e} outputs the union of the disjoint sets of changes +output by @option{-3} and @option{-x}. + +Output of @samp{diff3 -e lao tzu tao}: +@example +11a + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan +. +8c + so we may see their result. +. +@end example + +Output of @samp{diff3 -3 lao tzu tao}: +@example +8c + so we may see their result. +. +@end example + +Output of @samp{diff3 -x lao tzu tao}: +@example +11a + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan +. +@end example + +@node Marking Conflicts +@section Marking Conflicts +@cindex conflict marking +@cindex @samp{<<<<<<<} for marking conflicts + +@command{diff3} can mark conflicts in the merged output by +bracketing them with special marker lines. A conflict +that comes from two files @var{A} and @var{B} is marked as follows: + +@example +<<<<<<< @var{A} +@r{lines from @var{A}} +======= +@r{lines from @var{B}} +>>>>>>> @var{B} +@end example + +A conflict that comes from three files @var{A}, @var{B} and @var{C} is +marked as follows: + +@example +<<<<<<< @var{A} +@r{lines from @var{A}} +||||||| @var{B} +@r{lines from @var{B}} +======= +@r{lines from @var{C}} +>>>>>>> @var{C} +@end example + +The @option{-A} or @option{--show-all} option acts like the @option{-e} +option, except that it brackets conflicts, and it outputs all changes +from @var{older} to @var{yours}, not just the unmerged changes. Thus, +given the sample input files (@pxref{Sample diff3 Input}), @samp{diff3 +-A lao tzu tao} puts brackets around the conflict where only @file{tzu} +differs: + +@example +<<<<<<< tzu +======= +The Way that can be told of is not the eternal Way; +The name that can be named is not the eternal name. +>>>>>>> tao +@end example + +And it outputs the three-way conflict as follows: + +@example +<<<<<<< lao +||||||| tzu +They both may be called deep and profound. +Deeper and more profound, +The door of all subtleties! +======= + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan +>>>>>>> tao +@end example + +The @option{-E} or @option{--show-overlap} option outputs less information +than the @option{-A} or @option{--show-all} option, because it outputs only +unmerged changes, and it never outputs the contents of the second +file. Thus the @option{-E} option acts like the @option{-e} option, +except that it brackets the first and third files from three-way +overlapping changes. Similarly, @option{-X} acts like @option{-x}, except +it brackets all its (necessarily overlapping) changes. For example, +for the three-way overlapping change above, the @option{-E} and @option{-X} +options output the following: + +@example +<<<<<<< lao +======= + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan +>>>>>>> tao +@end example + +If you are comparing files that have meaningless or uninformative names, +you can use the @option{-L @var{label}} or @option{--label=@var{label}} +option to show alternate names in the @samp{<<<<<<<}, @samp{|||||||} +and @samp{>>>>>>>} brackets. This option can be given up to three +times, once for each input file. Thus @samp{diff3 -A -L X -L Y -L Z A +B C} acts like @samp{diff3 -A A B C}, except that the output looks like +it came from files named @samp{X}, @samp{Y} and @samp{Z} rather than +from files named @samp{A}, @samp{B} and @samp{C}. + +@node Bypassing ed +@section Generating the Merged Output Directly +@cindex merged @command{diff3} format + +With the @option{-m} or @option{--merge} option, @command{diff3} outputs the +merged file directly. This is more efficient than using @command{ed} to +generate it, and works even with non-text files that @command{ed} would +reject. If you specify @option{-m} without an @command{ed} script option, +@option{-A} (@option{--show-all}) is assumed. + +For example, the command @samp{diff3 -m lao tzu tao} +(@pxref{Sample diff3 Input} for a copy of the input files) would output +the following: + +@example +<<<<<<< tzu +======= +The Way that can be told of is not the eternal Way; +The name that can be named is not the eternal name. +>>>>>>> tao +The Nameless is the origin of Heaven and Earth; +The Named is the mother of all things. +Therefore let there always be non-being, + so we may see their subtlety, +And let there always be being, + so we may see their result. +The two are the same, +But after they are produced, + they have different names. +<<<<<<< lao +||||||| tzu +They both may be called deep and profound. +Deeper and more profound, +The door of all subtleties! +======= + + -- The Way of Lao-Tzu, tr. Wing-tsit Chan +>>>>>>> tao +@end example + +@node Merging Incomplete Lines +@section How @command{diff3} Merges Incomplete Lines +@cindex incomplete line merging + +With @option{-m}, incomplete lines (@pxref{Incomplete Lines}) are simply +copied to the output as they are found; if the merged output ends in an +conflict and one of the input files ends in an incomplete +line, succeeding @samp{|||||||}, @samp{=======} or @samp{>>>>>>>} +brackets appear somewhere other than the start of a line because +they are appended to the incomplete line. + +Without @option{-m}, if an @command{ed} script option is specified and an +incomplete line is found, @command{diff3} generates a warning and acts as +if a newline had been present. + +@node Saving the Changed File +@section Saving the Changed File +@cindex System V @command{diff3} compatibility + +Traditional Unix @command{diff3} generates an @command{ed} script without the +trailing @samp{w} and @samp{q} commands that save the changes. +System V @command{diff3} generates these extra commands. @sc{gnu} +@command{diff3} normally behaves like traditional Unix +@command{diff3}, but with the @option{-i} option it behaves like +System V @command{diff3} and appends the @samp{w} and @samp{q} +commands. + +The @option{-i} option requires one of the @command{ed} script options +@option{-AeExX3}, and is incompatible with the merged output option +@option{-m}. + +@node Interactive Merging +@chapter Interactive Merging with @command{sdiff} +@cindex diff merging +@cindex interactive merging + +With @command{sdiff}, you can merge two files interactively based on a +side-by-side @option{-y} format comparison (@pxref{Side by Side}). Use +@option{-o @var{file}} or @option{--output=@var{file}} to specify where to +put the merged text. @xref{Invoking sdiff}, for more details on the +options to @command{sdiff}. + +Another way to merge files interactively is to use the Emacs Lisp +package @command{emerge}. @xref{emerge, , emerge, emacs, The @sc{gnu} Emacs +Manual}, for more information. + +@menu +* sdiff Option Summary:: Summary of @command{sdiff} options. +* Merge Commands:: Merging two files interactively. +@end menu + +@node sdiff Option Summary +@section Specifying @command{diff} Options to @command{sdiff} +@cindex @command{sdiff} output format + +The following @command{sdiff} options have the same meaning as for +@command{diff}. @xref{diff Options}, for the use of these options. + +@example +-a -b -d -i -t -v +-B -E -I @var{regexp} + +--ignore-blank-lines --ignore-case +--ignore-matching-lines=@var{regexp} --ignore-space-change +--ignore-tab-expansion +--left-column --minimal --speed-large-files +--strip-trailing-cr --suppress-common-lines --expand-tabs +--text --version --width=@var{columns} +@end example + +For historical reasons, @command{sdiff} has alternate names for some +options. The @option{-l} option is equivalent to the +@option{--left-column} option, and similarly @option{-s} is equivalent +to @option{--suppress-common-lines}. The meaning of the @command{sdiff} +@option{-w} and @option{-W} options is interchanged from that of +@command{diff}: with @command{sdiff}, @option{-w @var{columns}} is +equivalent to @option{--width=@var{columns}}, and @option{-W} is +equivalent to @option{--ignore-all-space}. @command{sdiff} without the +@option{-o} option is equivalent to @command{diff} with the @option{-y} +or @option{--side-by-side} option (@pxref{Side by Side}). + +@node Merge Commands +@section Merge Commands +@cindex merge commands +@cindex merging interactively + +Groups of common lines, with a blank gutter, are copied from the first +file to the output. After each group of differing lines, @command{sdiff} +prompts with @samp{%} and pauses, waiting for one of the following +commands. Follow each command with @key{RET}. + +@table @samp +@item e +Discard both versions. +Invoke a text editor on an empty temporary file, +then copy the resulting file to the output. + +@item eb +Concatenate the two versions, edit the result in a temporary file, +then copy the edited result to the output. + +@item ed +Like @samp{eb}, except precede each version with a header that +shows what file and lines the version came from. + +@item el +Edit a copy of the left version, then copy the result to the output. + +@item er +Edit a copy of the right version, then copy the result to the output. + +@item l +Copy the left version to the output. + +@item q +Quit. + +@item r +Copy the right version to the output. + +@item s +Silently copy common lines. + +@item v +Verbosely copy common lines. This is the default. +@end table + +@vindex EDITOR +The text editor invoked is specified by the @env{EDITOR} environment +variable if it is set. The default is system-dependent. + +@node Merging with patch +@chapter Merging with @command{patch} + +@command{patch} takes comparison output produced by @command{diff} and applies +the differences to a copy of the original file, producing a patched +version. With @command{patch}, you can distribute just the changes to a +set of files instead of distributing the entire file set; your +correspondents can apply @command{patch} to update their copy of the files +with your changes. @command{patch} automatically determines the diff +format, skips any leading or trailing headers, and uses the headers to +determine which file to patch. This lets your correspondents feed a +mail message containing a difference listing directly to +@command{patch}. + +@command{patch} detects and warns about common problems like forward +patches. It saves any patches that it could not apply. It can also maintain a +@code{patchlevel.h} file to ensure that your correspondents apply +diffs in the proper order. + +@command{patch} accepts a series of diffs in its standard input, usually +separated by headers that specify which file to patch. It applies +@command{diff} hunks (@pxref{Hunks}) one by one. If a hunk does not +exactly match the original file, @command{patch} uses heuristics to try to +patch the file as well as it can. If no approximate match can be found, +@command{patch} rejects the hunk and skips to the next hunk. @command{patch} +normally replaces each file @var{f} with its new version, putting reject +hunks (if any) into @samp{@var{f}.rej}. + +@xref{Invoking patch}, for detailed information on the options to +@command{patch}. + +@menu +* patch Input:: Selecting the type of @command{patch} input. +* Revision Control:: Getting files from @sc{rcs}, @sc{sccs}, etc. +* Imperfect:: Dealing with imperfect patches. +* Creating and Removing:: Creating and removing files with a patch. +* Patching Time Stamps:: Updating time stamps on patched files. +* Multiple Patches:: Handling multiple patches in a file. +* patch Directories:: Changing directory and stripping directories. +* Backups:: Whether backup files are made. +* Backup Names:: Backup file names. +* Reject Names:: Reject file names. +* patch Messages:: Messages and questions @command{patch} can produce. +* patch and POSIX:: Conformance to the @sc{posix} standard. +* patch and Tradition:: @sc{gnu} versus traditional @command{patch}. +@end menu + +@node patch Input +@section Selecting the @command{patch} Input Format +@cindex @command{patch} input format + +@command{patch} normally determines which @command{diff} format the patch +file uses by examining its contents. For patch files that contain +particularly confusing leading text, you might need to use one of the +following options to force @command{patch} to interpret the patch file as a +certain format of diff. The output formats listed here are the only +ones that @command{patch} can understand. + +@table @option +@item -c +@itemx --context +context diff. + +@item -e +@itemx --ed +@command{ed} script. + +@item -n +@itemx --normal +normal diff. + +@item -u +@itemx --unified +unified diff. +@end table + +@node Revision Control +@section Revision Control +@cindex revision control +@cindex version control +@cindex @sc{rcs} +@cindex ClearCase +@cindex @sc{sccs} + +If a nonexistent input file is under a revision control system +supported by @command{patch}, @command{patch} normally asks the user +whether to get (or check out) the file from the revision control +system. Patch currently supports @sc{rcs}, ClearCase and @sc{sccs}. +Under @sc{rcs} and @sc{sccs}, @command{patch} also asks when the input +file is read-only and matches the default version in the revision +control system. + +@vindex PATCH_GET +The @option{-g @var{num}} or @option{--get=@var{num}} affects access +to files under supported revision control systems. If @var{num} is +positive, @command{patch} gets the file without asking the user; if +zero, @command{patch} neither asks the user nor gets the file; and if +negative, @command{patch} asks the user before getting the file. The +default value of @var{num} is given by the value of the +@env{PATCH_GET} environment variable if it is set; if not, the default +value is zero if @command{patch} is conforming to @sc{posix}, negative +otherwise. @xref{patch and POSIX}. + +@vindex VERSION_CONTROL +The choice of revision control system is unaffected by the +@env{VERSION_CONTROL} environment variable (@pxref{Backup Names}). + +@node Imperfect +@section Applying Imperfect Patches +@cindex imperfect patch application + +@command{patch} tries to skip any leading text in the patch file, +apply the diff, and then skip any trailing text. Thus you can feed a +mail message directly to @command{patch}, and it should work. If the +entire diff is indented by a constant amount of white space, +@command{patch} automatically ignores the indentation. If a context +diff contains trailing carriage return on each line, @command{patch} +automatically ignores the carriage return. If a context diff has been +encapsulated by prepending @w{@samp{- }} to lines beginning with @samp{-} +as per @uref{ftp://ftp.isi.edu/in-notes/rfc934.txt, Internet RFC 934}, +@command{patch} automatically unencapsulates the input. + +However, certain other types of imperfect input require user +intervention or testing. + +@menu +* Changed White Space:: When tabs and spaces don't match exactly. +* Reversed Patches:: Applying reversed patches correctly. +* Inexact:: Helping @command{patch} find close matches. +* Dry Runs:: Predicting what @command{patch} will do. +@end menu + +@node Changed White Space +@subsection Applying Patches with Changed White Space +@cindex white space in patches + +Sometimes mailers, editors, or other programs change spaces into tabs, +or vice versa. If this happens to a patch file or an input file, the +files might look the same, but @command{patch} will not be able to match +them properly. If this problem occurs, use the @option{-l} or +@option{--ignore-white-space} option, which makes @command{patch} compare +blank characters (i.e.@: spaces and tabs) loosely so that any nonempty +sequence of blanks in the patch file matches any nonempty sequence of +blanks in the input files. Non-blank +characters must still match exactly. Each line of the context must +still match a line in the input file. + +@node Reversed Patches +@subsection Applying Reversed Patches +@cindex reversed patches + +Sometimes people run @command{diff} with the new file first instead of +second. This creates a diff that is ``reversed''. To apply such +patches, give @command{patch} the @option{-R} or @option{--reverse} option. +@command{patch} then attempts to swap each hunk around before applying it. +Rejects come out in the swapped format. + +Often @command{patch} can guess that the patch is reversed. If the first +hunk of a patch fails, @command{patch} reverses the hunk to see if it can +apply it that way. If it can, @command{patch} asks you if you want to have +the @option{-R} option set; if it can't, @command{patch} continues to apply +the patch normally. This method cannot detect a reversed patch if it is +a normal diff and the first command is an append (which should have been +a delete) since appends always succeed, because a null context matches +anywhere. But most patches add or change lines rather than delete them, +so most reversed normal diffs begin with a delete, which fails, and +@command{patch} notices. + +If you apply a patch that you have already applied, @command{patch} thinks +it is a reversed patch and offers to un-apply the patch. This could be +construed as a feature. If you did this inadvertently and you don't +want to un-apply the patch, just answer @samp{n} to this offer and to +the subsequent ``apply anyway'' question---or type @kbd{C-c} to kill the +@command{patch} process. + +@node Inexact +@subsection Helping @command{patch} Find Inexact Matches +@cindex inexact patches +@cindex fuzz factor when patching + +For context diffs, and to a lesser extent normal diffs, @command{patch} can +detect when the line numbers mentioned in the patch are incorrect, and +it attempts to find the correct place to apply each hunk of the patch. +As a first guess, it takes the line number mentioned in the hunk, plus +or minus any offset used in applying the previous hunk. If that is not +the correct place, @command{patch} scans both forward and backward for a +set of lines matching the context given in the hunk. + +First @command{patch} looks for a place where all lines of the context +match. If it cannot find such a place, and it is reading a context or +unified diff, and the maximum fuzz factor is set to 1 or more, then +@command{patch} makes another scan, ignoring the first and last line of +context. If that fails, and the maximum fuzz factor is set to 2 or +more, it makes another scan, ignoring the first two and last two lines +of context are ignored. It continues similarly if the maximum fuzz +factor is larger. + +The @option{-F @var{lines}} or @option{--fuzz=@var{lines}} option sets the +maximum fuzz factor to @var{lines}. This option only applies to context +and unified diffs; it ignores up to @var{lines} lines while looking for +the place to install a hunk. Note that a larger fuzz factor increases +the odds of making a faulty patch. The default fuzz factor is 2; there +is no point to setting it to more than the number of lines of context +in the diff, ordinarily 3. + +If @command{patch} cannot find a place to install a hunk of the patch, it +writes the hunk out to a reject file (@pxref{Reject Names}, for information +on how reject files are named). It writes out rejected hunks in context +format no matter what form the input patch is in. If the input is a +normal or @command{ed} diff, many of the contexts are simply null. The +line numbers on the hunks in the reject file may be different from those +in the patch file: they show the approximate location where @command{patch} +thinks the failed hunks belong in the new file rather than in the old +one. + +If the @option{--verbose} option is given, then +as it completes each hunk @command{patch} tells you whether the hunk +succeeded or failed, and if it failed, on which line (in the new file) +@command{patch} thinks the hunk should go. If this is different from the +line number specified in the diff, it tells you the offset. A single +large offset @emph{may} indicate that @command{patch} installed a hunk in +the wrong place. @command{patch} also tells you if it used a fuzz factor +to make the match, in which case you should also be slightly suspicious. + +@command{patch} cannot tell if the line numbers are off in an @command{ed} +script, and can only detect wrong line numbers in a normal diff when it +finds a change or delete command. It may have the same problem with a +context diff using a fuzz factor equal to or greater than the number of +lines of context shown in the diff (typically 3). In these cases, you +should probably look at a context diff between your original and patched +input files to see if the changes make sense. Compiling without errors +is a pretty good indication that the patch worked, but not a guarantee. + +A patch against an empty file applies to a nonexistent file, and vice +versa. @xref{Creating and Removing}. + +@command{patch} usually produces the correct results, even when it must +make many guesses. However, the results are guaranteed only when +the patch is applied to an exact copy of the file that the patch was +generated from. + +@node Dry Runs +@subsection Predicting what @command{patch} will do +@cindex testing @command{patch} +@cindex dry runs for @command{patch} + +It may not be obvious in advance what @command{patch} will do with a +complicated or poorly formatted patch. If you are concerned that the +input might cause @command{patch} to modify the wrong files, you can +use the @option{--dry-run} option, which causes @command{patch} to +print the results of applying patches without actually changing any +files. You can then inspect the diagnostics generated by the dry run +to see whether @command{patch} will modify the files that you expect. +If the patch does not do what you want, you can modify the patch (or +the other options to @command{patch}) and try another dry run. Once +you are satisfied with the proposed patch you can apply it by invoking +@command{patch} as before, but this time without the +@option{--dry-run} option. + +@node Creating and Removing +@section Creating and Removing Files +@cindex creating files +@cindex empty files, removing +@cindex removing empty files + +Sometimes when comparing two directories, a file may exist in one +directory but not the other. If you give @command{diff} the +@option{-N} or @option{--new-file} option, or if you supply an old or +new file that is named @file{/dev/null} or is empty and is dated the +Epoch (1970-01-01 00:00:00 UTC), @command{diff} outputs a patch that +adds or deletes the contents of this file. When given such a patch, +@command{patch} normally creates a new file or removes the old file. +However, when conforming to @sc{posix} (@pxref{patch and POSIX}), +@command{patch} does not remove the old file, but leaves it empty. +The @option{-E} or @option{--remove-empty-files} option causes +@command{patch} to remove output files that are empty after applying a +patch, even if the patch does not appear to be one that removed the +file. + +If the patch appears to create a file that already exists, +@command{patch} asks for confirmation before applying the patch. + +@node Patching Time Stamps +@section Updating Time Stamps on Patched Files +@cindex time stamps on patched files + +When @command{patch} updates a file, it normally sets the file's +last-modified time stamp to the current time of day. If you are using +@command{patch} to track a software distribution, this can cause +@command{make} to incorrectly conclude that a patched file is out of +date. For example, if @file{syntax.c} depends on @file{syntax.y}, and +@command{patch} updates @file{syntax.c} and then @file{syntax.y}, then +@file{syntax.c} will normally appear to be out of date with respect to +@file{syntax.y} even though its contents are actually up to date. + +The @option{-Z} or @option{--set-utc} option causes @command{patch} to +set a patched file's modification and access times to the time stamps +given in context diff headers. If the context diff headers do not +specify a time zone, they are assumed to use Coordinated Universal +Time (@sc{utc}, often known as @sc{gmt}). + +The @option{-T} or @option{--set-time} option acts like @option{-Z} or +@option{--set-utc}, except that it assumes that the context diff +headers' time stamps use local time instead of @sc{utc}. This option +is not recommended, because patches using local time cannot easily be +used by people in other time zones, and because local time stamps are +ambiguous when local clocks move backwards during daylight-saving time +adjustments. If the context diff headers specify a time zone, this +option is equivalent to @option{-Z} or @option{--set-utc}. + +@command{patch} normally refrains from setting a file's time stamps if +the file's original last-modified time stamp does not match the time +given in the diff header, of if the file's contents do not exactly +match the patch. However, if the @option{-f} or @option{--force} +option is given, the file's time stamps are set regardless. + +Due to the limitations of the current @command{diff} format, +@command{patch} cannot update the times of files whose contents have +not changed. Also, if you set file time stamps to values other than +the current time of day, you should also remove (e.g., with @samp{make +clean}) all files that depend on the patched files, so that later +invocations of @command{make} do not get confused by the patched +files' times. + +@node Multiple Patches +@section Multiple Patches in a File +@cindex multiple patches +@cindex intuiting file names from patches + +If the patch file contains more than one patch, and if you do not +specify an input file on the command line, @command{patch} tries to +apply each patch as if they came from separate patch files. This +means that it determines the name of the file to patch for each patch, +and that it examines the leading text before each patch for file names +and prerequisite revision level (@pxref{Making Patches}, for more on +that topic). + +@command{patch} uses the following rules to intuit a file name from +the leading text before a patch. First, @command{patch} takes an +ordered list of candidate file names as follows: + +@itemize @bullet +@item +If the header is that of a context diff, @command{patch} takes the old +and new file names in the header. A name is ignored if it does not +have enough slashes to satisfy the @option{-p@var{num}} or +@option{--strip=@var{num}} option. The name @file{/dev/null} is also +ignored. + +@item +If there is an @samp{Index:} line in the leading garbage and if either +the old and new names are both absent or if @command{patch} is +conforming to @sc{posix}, @command{patch} takes the name in the +@samp{Index:} line. + +@item +For the purpose of the following rules, the candidate file names are +considered to be in the order (old, new, index), regardless of the +order that they appear in the header. +@end itemize + +@noindent +Then @command{patch} selects a file name from the candidate list as +follows: + +@itemize @bullet +@item +If some of the named files exist, @command{patch} selects the first +name if conforming to @sc{posix}, and the best name otherwise. + +@item +If @command{patch} is not ignoring @sc{rcs}, ClearCase, and @sc{sccs} +(@pxref{Revision Control}), and no named files exist but an @sc{rcs}, +ClearCase, or @sc{sccs} master is found, @command{patch} selects the +first named file with an @sc{rcs}, ClearCase, or @sc{sccs} master. + +@item +If no named files exist, no @sc{rcs}, ClearCase, or @sc{sccs} master +was found, some names are given, @command{patch} is not conforming to +@sc{posix}, and the patch appears to create a file, @command{patch} +selects the best name requiring the creation of the fewest +directories. + +@item +If no file name results from the above heuristics, you are asked for +the name of the file to patch, and @command{patch} selects that name. +@end itemize + +To determine the @dfn{best} of a nonempty list of file names, +@command{patch} first takes all the names with the fewest path name +components; of those, it then takes all the names with the shortest +basename; of those, it then takes all the shortest names; finally, it +takes the first remaining name. + +@xref{patch and POSIX}, to see whether @command{patch} is conforming +to @sc{posix}. + +@node patch Directories +@section Applying Patches in Other Directories +@cindex directories and patch +@cindex patching directories + +The @option{-d @var{directory}} or @option{--directory=@var{directory}} +option to @command{patch} makes directory @var{directory} the current +directory for interpreting both file names in the patch file, and file +names given as arguments to other options (such as @option{-B} and +@option{-o}). For example, while in a mail reading program, you can patch +a file in the @file{/usr/src/emacs} directory directly from a message +containing the patch like this: + +@example +| patch -d /usr/src/emacs +@end example + +Sometimes the file names given in a patch contain leading directories, +but you keep your files in a directory different from the one given in +the patch. In those cases, you can use the +@option{-p@var{number}} or @option{--strip=@var{number}} +option to set the file name strip count to @var{number}. The strip +count tells @command{patch} how many slashes, along with the directory +names between them, to strip from the front of file names. A sequence +of one or more adjacent slashes is counted as a single slash. By +default, @command{patch} strips off all leading directories, leaving +just the base file names. + +For example, suppose the file name in the patch file is +@file{/gnu/src/emacs/etc/NEWS}. Using @option{-p0} gives the +entire file name unmodified, @option{-p1} gives +@file{gnu/src/emacs/etc/NEWS} (no leading slash), @option{-p4} gives +@file{etc/NEWS}, and not specifying @option{-p} at all gives @file{NEWS}. + +@command{patch} looks for each file (after any slashes have been stripped) +in the current directory, or if you used the @option{-d @var{directory}} +option, in that directory. + +@node Backups +@section Backup Files +@cindex backup file strategy + +Normally, @command{patch} creates a backup file if the patch does not +exactly match the original input file, because in that case the +original data might not be recovered if you undo the patch with +@samp{patch -R} (@pxref{Reversed Patches}). However, when conforming +to @sc{posix}, @command{patch} does not create backup files by +default. @xref{patch and POSIX}. + +The @option{-b} or @option{--backup} option causes @command{patch} to +make a backup file regardless of whether the patch matches the +original input. The @option{--backup-if-mismatch} option causes +@command{patch} to create backup files for mismatches files; this is +the default when not conforming to @sc{posix}. The +@option{--no-backup-if-mismatch} option causes @command{patch} to not +create backup files, even for mismatched patches; this is the default +when conforming to @sc{posix}. + +When backing up a file that does not exist, an empty, unreadable +backup file is created as a placeholder to represent the nonexistent +file. + +@node Backup Names +@section Backup File Names +@cindex backup file names + +Normally, @command{patch} renames an original input file into a backup +file by appending to its name the extension @samp{.orig}, or @samp{~} +if using @samp{.orig} would make the backup file name too +long.@footnote{A coding error in @sc{gnu} @command{patch} version +2.5.4 causes it to always use @samp{~}, but this should be fixed in +the next release.} The @option{-z @var{backup-suffix}} or +@option{--suffix=@var{backup-suffix}} option causes @command{patch} to +use @var{backup-suffix} as the backup extension instead. + +@vindex SIMPLE_BACKUP_SUFFIX +Alternately, you can specify the extension for backup files with the +@env{SIMPLE_BACKUP_SUFFIX} environment variable, which the options +override. + +@command{patch} can also create numbered backup files the way @sc{gnu} Emacs +does. With this method, instead of having a single backup of each file, +@command{patch} makes a new backup file name each time it patches a file. +For example, the backups of a file named @file{sink} would be called, +successively, @file{sink.~1~}, @file{sink.~2~}, @file{sink.~3~}, etc. + +@vindex PATCH_VERSION_CONTROL +@vindex VERSION_CONTROL +The @option{-V @var{backup-style}} or +@option{--version-control=@var{backup-style}} option takes as an +argument a method for creating backup file names. You can alternately +control the type of backups that @command{patch} makes with the +@env{PATCH_VERSION_CONTROL} environment variable, which the +@option{-V} option overrides. If @env{PATCH_VERSION_CONTROL} is not +set, the @env{VERSION_CONTROL} environment variable is used instead. +Please note that these options and variables control backup file +names; they do not affect the choice of revision control system +(@pxref{Revision Control}). + +The values of these environment variables and the argument to the +@option{-V} option are like the @sc{gnu} Emacs @code{version-control} +variable (@pxref{Backup Names, , , emacs, The @sc{gnu} Emacs Manual}, +for more information on backup versions in Emacs). They also +recognize synonyms that are more descriptive. The valid values are +listed below; unique abbreviations are acceptable. + +@table @option +@item t +@itemx numbered +Always make numbered backups. + +@item nil +@itemx existing +Make numbered backups of files that already have them, simple backups of +the others. This is the default. + +@item never +@itemx simple +Always make simple backups. +@end table + +You can also tell @command{patch} to prepend a prefix, such as a +directory name, to produce backup file names. The @option{-B +@var{prefix}} or @option{--prefix=@var{prefix}} option makes backup +files by prepending @var{prefix} to them. The @option{-Y +@var{prefix}} or @option{--basename-prefix=@var{prefix}} prepends +@var{prefix} to the last file name component of backup file names +instead; for example, @option{-Y ~} causes the backup name for +@file{dir/file.c} to be @file{dir/~file.c}. If you use either of +these prefix options, the suffix-based options are ignored. + +If you specify the output file with the @option{-o} option, that file is +the one that is backed up, not the input file. + +Options that affect the names of backup files do not affect whether +backups are made. For example, if you specify the +@option{--no-backup-if-mismatch} option, none of the options described +in this section have any affect, because no backups are made. + +@node Reject Names +@section Reject File Names +@cindex reject file names + +The names for reject files (files containing patches that +@command{patch} could not find a place to apply) are normally the name +of the output file with @samp{.rej} appended (or @samp{#} if if using +@samp{.rej} would make the backup file name too long). + +Alternatively, you can tell @command{patch} to place all of the rejected +patches in a single file. The @option{-r @var{reject-file}} or +@option{--reject-file=@var{reject-file}} option uses @var{reject-file} as +the reject file name. + +@node patch Messages +@section Messages and Questions from @command{patch} +@cindex @command{patch} messages and questions +@cindex diagnostics from @command{patch} +@cindex messages from @command{patch} + +@command{patch} can produce a variety of messages, especially if it +has trouble decoding its input. In a few situations where it's not +sure how to proceed, @command{patch} normally prompts you for more +information from the keyboard. There are options to produce more or +fewer messages, to have it not ask for keyboard input, and to +affect the way that file names are quoted in messages. + +@menu +* More or Fewer Messages:: Controlling the verbosity of @command{patch}. +* patch and Keyboard Input:: Inhibiting keyboard input. +* patch Quoting Style:: Quoting file names in diagnostics. +@end menu + +@command{patch} exits with status 0 if all hunks are applied successfully, +1 if some hunks cannot be applied, and 2 if there is more serious trouble. +When applying a set of patches in a loop, you should check the +exit status, so you don't apply a later patch to a partially patched +file. + +@node More or Fewer Messages +@subsection Controlling the Verbosity of @command{patch} +@cindex verbose messages from @command{patch} +@cindex inhibit messages from @command{patch} + +You can cause @command{patch} to produce more messages by using the +@option{--verbose} option. For example, when you give this option, +the message @samp{Hmm...} indicates that @command{patch} is reading text in +the patch file, attempting to determine whether there is a patch in that +text, and if so, what kind of patch it is. + +You can inhibit all terminal output from @command{patch}, unless an error +occurs, by using the @option{-s}, @option{--quiet}, or @option{--silent} +option. + +@node patch and Keyboard Input +@subsection Inhibiting Keyboard Input +@cindex keyboard input to @command{patch} + +There are two ways you can prevent @command{patch} from asking you any +questions. The @option{-f} or @option{--force} option assumes that you know +what you are doing. It causes @command{patch} to do the following: + +@itemize @bullet +@item +Skip patches that do not contain file names in their headers. + +@item +Patch files even though they have the wrong version for the +@samp{Prereq:} line in the patch; + +@item +Assume that patches are not reversed even if they look like they are. +@end itemize + +@noindent +The @option{-t} or @option{--batch} option is similar to @option{-f}, in that +it suppresses questions, but it makes somewhat different assumptions: + +@itemize @bullet +@item +Skip patches that do not contain file names in their headers +(the same as @option{-f}). + +@item +Skip patches for which the file has the wrong version for the +@samp{Prereq:} line in the patch; + +@item +Assume that patches are reversed if they look like they are. +@end itemize + +@node patch Quoting Style +@subsection @command{patch} Quoting Style +@cindex quoting style + +When @command{patch} outputs a file name in a diagnostic message, it +can format the name in any of several ways. This can be useful to +output file names unambiguously, even if they contain punctuation or +special characters like newlines. The +@option{--quoting-style=@var{word}} option controls how names are +output. The @var{word} should be one of the following: + +@table @samp +@item literal +Output names as-is. +@item shell +Quote names for the shell if they contain shell metacharacters or would +cause ambiguous output. +@item shell-always +Quote names for the shell, even if they would normally not require quoting. +@item c +Quote names as for a C language string. +@item escape +Quote as with @samp{c} except omit the surrounding double-quote +characters. +@c The following are not yet implemented in patch 2.5.4. +@c @item clocale +@c Quote as with @samp{c} except use quotation marks appropriate for the +@c locale. +@c @item locale +@c @c Use @t instead of @samp to avoid duplicate quoting in some output styles. +@c Like @samp{clocale}, but quote @t{`like this'} instead of @t{"like +@c this"} in the default C locale. This looks nicer on many displays. +@end table + +@vindex QUOTING_STYLE +You can specify the default value of the @option{--quoting-style} +option with the environment variable @env{QUOTING_STYLE}. If that +environment variable is not set, the default value is @samp{shell}, +but this default may change in a future version of @command{patch}. + +@node patch and POSIX +@section @command{patch} and the @sc{posix} Standard +@cindex @sc{posix} + +@vindex POSIXLY_CORRECT +If you specify the @option{--posix} option, or set the +@env{POSIXLY_CORRECT} environment variable, @command{patch} conforms +more strictly to the @sc{posix} standard, as follows: + +@itemize @bullet +@item +Take the first existing file from the list (old, new, index) +when intuiting file names from diff headers. @xref{Multiple Patches}. + +@item +Do not remove files that are removed by a diff. +@xref{Creating and Removing}. + +@item +Do not ask whether to get files from @sc{rcs}, ClearCase, or +@sc{sccs}. @xref{Revision Control}. + +@item +Require that all options precede the files in the command line. + +@item +Do not backup files, even when there is a mismatch. @xref{Backups}. + +@end itemize + +@node patch and Tradition +@section @sc{gnu} @command{patch} and Traditional @command{patch} +@cindex traditional @command{patch} + +The current version of @sc{gnu} @command{patch} normally follows the +@sc{posix} standard. @xref{patch and POSIX}, for the few exceptions +to this general rule. + +Unfortunately, @sc{posix} redefined the behavior of @command{patch} in +several important ways. You should be aware of the following +differences if you must interoperate with traditional @command{patch}, +or with @sc{gnu} @command{patch} version 2.1 and earlier. + +@itemize @bullet +@item +In traditional @command{patch}, the @option{-p} option's operand was +optional, and a bare @option{-p} was equivalent to @option{-p0}. The +@option{-p} option now requires an operand, and @option{-p@ 0} is now +equivalent to @option{-p0}. For maximum compatibility, use options +like @option{-p0} and @option{-p1}. + +Also, traditional @command{patch} simply counted slashes when +stripping path prefixes; @command{patch} now counts pathname +components. That is, a sequence of one or more adjacent slashes now +counts as a single slash. For maximum portability, avoid sending +patches containing @file{//} in file names. + +@item +In traditional @command{patch}, backups were enabled by default. This +behavior is now enabled with the @option{-b} or @option{--backup} +option. + +Conversely, in @sc{posix} @command{patch}, backups are never made, +even when there is a mismatch. In @sc{gnu} @command{patch}, this +behavior is enabled with the @option{--no-backup-if-mismatch} option, +or by conforming to @sc{posix}. + +The @option{-b@ @var{suffix}} option of traditional @command{patch} is +equivalent to the @samp{-b -z@ @var{suffix}} options of @sc{gnu} +@command{patch}. + +@item +Traditional @command{patch} used a complicated (and incompletely +documented) method to intuit the name of the file to be patched from +the patch header. This method did not conform to @sc{posix}, and had +a few gotchas. Now @command{patch} uses a different, equally +complicated (but better documented) method that is optionally +@sc{posix}-conforming; we hope it has fewer gotchas. The two methods +are compatible if the file names in the context diff header and the +@samp{Index:} line are all identical after prefix-stripping. Your +patch is normally compatible if each header's file names all contain +the same number of slashes. + +@item +When traditional @command{patch} asked the user a question, it sent +the question to standard error and looked for an answer from the first +file in the following list that was a terminal: standard error, +standard output, @file{/dev/tty}, and standard input. Now +@command{patch} sends questions to standard output and gets answers +from @file{/dev/tty}. Defaults for some answers have been changed so +that @command{patch} never goes into an infinite loop when using +default answers. + +@item +Traditional @command{patch} exited with a status value that counted +the number of bad hunks, or with status 1 if there was real trouble. +Now @command{patch} exits with status 1 if some hunks failed, or with +2 if there was real trouble. + +@item +Limit yourself to the following options when sending instructions +meant to be executed by anyone running @sc{gnu} @command{patch}, +traditional @command{patch}, or a @command{patch} that conforms to +@sc{posix}. Spaces are significant in the following list, and +operands are required. + +@example +@option{-c} +@option{-d @var{dir}} +@option{-D @var{define}} +@option{-e} +@option{-l} +@option{-n} +@option{-N} +@option{-o @var{outfile}} +@option{-p@var{num}} +@option{-R} +@option{-r @var{rejectfile}} +@end example + +@end itemize + +@node Making Patches +@chapter Tips for Making and Using Patches + +Use some common sense when making and using patches. For example, +when sending bug fixes to a program's maintainer, send several small +patches, one per independent subject, instead of one large, +harder-to-digest patch that covers all the subjects. + +Here are some other things you should keep in mind if you are going to +distribute patches for updating a software package. + +@menu +* Tips for Patch Producers:: Advice for making patches. +* Tips for Patch Consumers:: Advice for using patches. +* Avoiding Common Mistakes:: Avoiding common mistakes when using @command{patch}. +* Generating Smaller Patches:: How to generate smaller patches. +@end menu + +@node Tips for Patch Producers +@section Tips for Patch Producers +@cindex patch producer tips + +To create a patch that changes an older version of a package into a +newer version, first make a copy of the older and newer versions in +adjacent subdirectories. It is common to do that by unpacking +@command{tar} archives of the two versions. + +To generate the patch, use the command @samp{diff -Naur @var{old} +@var{new}} where @var{old} and @var{new} identify the old and new +directories. The names @var{old} and @var{new} should not contain any +slashes. The @option{-N} option lets the patch create and remove +files; @option{-a} lets the patch update non-text files; @option{-u} +generates useful time stamps and enough context; and @option{-r} lets +the patch update subdirectories. Here is an example command, using +Bourne shell syntax: + +@example +diff -Naur gcc-3.0.3 gcc-3.0.4 +@end example + +Tell your recipients how to apply the patches. This should include +which working directory to use, and which @command{patch} options to +use; the option @samp{-p1} is recommended. Test your procedure by +pretending to be a recipient and applying your patches to a copy of +the original files. + +@xref{Avoiding Common Mistakes}, for how to avoid common mistakes when +generating a patch. + +@node Tips for Patch Consumers +@section Tips for Patch Consumers +@cindex patch consumer tips + +A patch producer should tell recipients how to apply the patches, so +the first rule of thumb for a patch consumer is to follow the +instructions supplied with the patch. + +@sc{gnu} @command{diff} can analyze files with arbitrarily long lines +and files that end in incomplete lines. However, older versions of +@command{patch} cannot patch such files. If you are having trouble +applying such patches, try upgrading to a recent version of @sc{gnu} +@command{patch}. + +@node Avoiding Common Mistakes +@section Avoiding Common Mistakes +@cindex common mistakes with patches +@cindex patch, common mistakes + +When producing a patch for multiple files, apply @command{diff} to +directories whose names do not have slashes. This reduces confusion +when the patch consumer specifies the @option{-p@var{number}} option, +since this option can have surprising results when the old and new +file names have different numbers of slashes. For example, do not +send a patch with a header that looks like this: + +@example +diff -Naur v2.0.29/prog/README prog/README +--- v2.0.29/prog/README 2002-03-10 23:30:39.942229878 -0800 ++++ prog/README 2002-03-17 20:49:32.442260588 -0800 +@end example + +@noindent +because the two file names have different numbers of slashes, and +different versions of @command{patch} interpret the file names +differently. To avoid confusion, send output that looks like this +instead: + +@example +diff -Naur v2.0.29/prog/README v2.0.30/prog/README +--- v2.0.29/prog/README 2002-03-10 23:30:39.942229878 -0800 ++++ v2.0.30/prog/README 2002-03-17 20:49:32.442260588 -0800 +@end example + +Make sure you have specified the file names correctly, either in a +context diff header or with an @samp{Index:} line. Take care to not send out +reversed patches, since these make people wonder whether they have +already applied the patch. + +Avoid sending patches that compare backup file names like +@file{README.orig} or @file{README~}, since this might confuse +@command{patch} into patching a backup file instead of the real file. +Instead, send patches that compare the same base file names in +different directories, e.g.@: @file{old/README} and @file{new/README}. + +To save people from partially applying a patch before other patches that +should have gone before it, you can make the first patch in the patch +file update a file with a name like @file{patchlevel.h} or +@file{version.c}, which contains a patch level or version number. If +the input file contains the wrong version number, @command{patch} will +complain immediately. + +An even clearer way to prevent this problem is to put a @samp{Prereq:} +line before the patch. If the leading text in the patch file contains a +line that starts with @samp{Prereq:}, @command{patch} takes the next word +from that line (normally a version number) and checks whether the next +input file contains that word, preceded and followed by either +white space or a newline. If not, @command{patch} prompts you for +confirmation before proceeding. This makes it difficult to accidentally +apply patches in the wrong order. + +@node Generating Smaller Patches +@section Generating Smaller Patches +@cindex patches, shrinking + +The simplest way to generate a patch is to use @samp{diff -Naur} +(@pxref{Tips for Patch Producers}), but you might be able to reduce +the size of the patch by renaming or removing some files before making +the patch. If the older version of the package contains any files +that the newer version does not, or if any files have been renamed +between the two versions, make a list of @command{rm} and @command{mv} +commands for the user to execute in the old version directory before +applying the patch. Then run those commands yourself in the scratch +directory. + +If there are any files that you don't need to include in the patch +because they can easily be rebuilt from other files (for example, +@file{TAGS} and output from @command{yacc} and @command{makeinfo}), +exclude them from the patch by giving @command{diff} the @option{-x +@var{pattern}} option (@pxref{Comparing Directories}). If you want +your patch to modify a derived file because your recipients lack tools +to build it, make sure that the patch for the derived file follows any +patches for files that it depends on, so that the recipients' time +stamps will not confuse @command{make}. + +Now you can create the patch using @samp{diff -Naur}. Make sure to +specify the scratch directory first and the newer directory second. + +Add to the top of the patch a note telling the user any @command{rm} and +@command{mv} commands to run before applying the patch. Then you can +remove the scratch directory. + +You can also shrink the patch size by using fewer lines of context, +but bear in mind that @command{patch} typically needs at least two +lines for proper operation when patches do not exactly match the input +files. + +@node Invoking cmp +@chapter Invoking @command{cmp} +@cindex invoking @command{cmp} +@cindex @command{cmp} invocation + +The @command{cmp} command compares two files, and if they differ, +tells the first byte and line number where they differ. Bytes and +lines are numbered starting with 1. The arguments of @command{cmp} +are as follows: + +@example +cmp @var{options}@dots{} @var{from-file} @r{[}@var{to-file} @r{[}@var{from-skip} @r{[}@var{to-skip}@r{]}@r{]}@r{]} +@end example + +The file name @file{-} is always the standard input. @command{cmp} +also uses the standard input if one file name is omitted. The +@var{from-skip} and @var{to-skip} operands specify how many bytes to +ignore at the start of each file; they are equivalent to the +@option{--ignore-initial=@var{from-skip}:@var{to-skip}} option. + +An exit status of 0 means no differences were found, 1 means some +differences were found, and 2 means trouble. + +@menu +* cmp Options:: Summary of options to @command{cmp}. +@end menu + +@node cmp Options +@section Options to @command{cmp} +@cindex @command{cmp} options +@cindex options for @command{cmp} + +Below is a summary of all of the options that @sc{gnu} @command{cmp} accepts. +Most options have two equivalent names, one of which is a single letter +preceded by @samp{-}, and the other of which is a long name preceded by +@samp{--}. Multiple single letter options (unless they take an +argument) can be combined into a single command line word: @option{-bl} is +equivalent to @option{-b -l}. + +@table @option +@item -b +@itemx --print-bytes +Print the differing bytes. Display control bytes as a +@samp{^} followed by a letter of the alphabet and precede bytes +that have the high bit set with @samp{M-} (which stands for ``meta''). + +@item --help +Output a summary of usage and then exit. + +@item -i @var{skip} +@itemx --ignore-initial=@var{skip} +Ignore any differences in the first @var{skip} bytes of the input +files. Treat files with fewer than @var{skip} bytes as if they are +empty. If @var{skip} is of the form +@option{@var{from-skip}:@var{to-skip}}, skip the first @var{from-skip} +bytes of the first input file and the first @var{to-skip} bytes of the +second. + +@item -l +@itemx --verbose +Print the (decimal) byte numbers and (octal) values of all differing bytes. + +@item -n @var{count} +@itemx --bytes=@var{count} +Compare at most @var{count} input bytes. + +@item -s +@itemx --quiet +@itemx --silent +Do not print anything; only return an exit status indicating whether +the files differ. + +@item -v +@itemx --version +Output version information and then exit. +@end table + +In the above table, operands that are byte counts are normally +decimal, but may be preceded by @samp{0} for octal and @samp{0x} for +hexadecimal. + +A byte count can be followed by a suffix to specify a multiple of that +count; in this case an omitted integer is understood to be 1. A bare +size letter, or one followed by @samp{iB}, specifies a multiple using +powers of 1024. A size letter followed by @samp{B} specifies powers +of 1000 instead. For example, @option{-n 4M} and @option{-n 4MiB} are +equivalent to @option{-n 4194304}, whereas @option{-n 4MB} is +equivalent to @option{-n 4000000}. This notation is upward compatible +with the @uref{http://www.bipm.fr/enus/3_SI/si-prefixes.html, SI +prefixes} for decimal multiples and with the +@uref{http://physics.nist.gov/cuu/Units/binary.html, IEC 60027-2 +prefixes for binary multiples}. + +The following suffixes are defined. Large sizes like @code{1Y} may be +rejected by your computer due to limitations of its arithmetic. + +@table @samp +@item kB +@cindex kilobyte, definition of +kilobyte: @math{10^3 = 1000}. +@item k +@itemx K +@itemx KiB +@cindex kibibyte, definition of +kibibyte: @math{2^10 = 1024}. @samp{K} is special: the SI prefix is +@samp{k} and the IEC 60027-2 prefix is @samp{Ki}, but tradition and +@sc{posix} use @samp{k} to mean @samp{KiB}. +@item MB +@cindex megabyte, definition of +megabyte: @math{10^6 = 1,000,000}. +@item M +@itemx MiB +@cindex mebibyte, definition of +mebibyte: @math{2^20 = 1,048,576}. +@item GB +@cindex gigabyte, definition of +gigabyte: @math{10^9 = 1,000,000,000}. +@item G +@itemx GiB +@cindex gibibyte, definition of +gibibyte: @math{2^30 = 1,073,741,824}. +@item TB +@cindex terabyte, definition of +terabyte: @math{10^12 = 1,000,000,000,000}. +@item T +@itemx TiB +@cindex tebibyte, definition of +tebibyte: @math{2^40 = 1,099,511,627,776}. +@item PB +@cindex petabyte, definition of +petabyte: @math{10^15 = 1,000,000,000,000,000}. +@item P +@itemx PiB +@cindex pebibyte, definition of +pebibyte: @math{2^50 = 1,125,899,906,842,624}. +@item EB +@cindex exabyte, definition of +exabyte: @math{10^18 = 1,000,000,000,000,000,000}. +@item E +@itemx EiB +@cindex exbibyte, definition of +exbibyte: @math{2^60 = 1,152,921,504,606,846,976}. +@item ZB +@cindex zettabyte, definition of +zettabyte: @math{10^21 = 1,000,000,000,000,000,000,000} +@item Z +@itemx ZiB +@math{2^70 = 1,180,591,620,717,411,303,424}. +(@samp{Zi} is a GNU extension to IEC 60027-2.) +@item YB +@cindex yottabyte, definition of +yottabyte: @math{10^24 = 1,000,000,000,000,000,000,000,000}. +@item Y +@itemx YiB +@math{2^80 = 1,208,925,819,614,629,174,706,176}. +(@samp{Yi} is a GNU extension to IEC 60027-2.) +@end table + +@node Invoking diff +@chapter Invoking @command{diff} +@cindex invoking @command{diff} +@cindex @command{diff} invocation + +The format for running the @command{diff} command is: + +@example +diff @var{options}@dots{} @var{files}@dots{} +@end example + +In the simplest case, two file names @var{from-file} and +@var{to-file} are given, and @command{diff} compares the contents of +@var{from-file} and @var{to-file}. A file name of @file{-} stands for +text read from the standard input. As a special case, @samp{diff - -} +compares a copy of standard input to itself. + +If one file is a directory and the other is not, @command{diff} compares +the file in the directory whose name is that of the non-directory. +The non-directory file must not be @file{-}. + +If two file names are given and both are directories, +@command{diff} compares corresponding files in both directories, in +alphabetical order; this comparison is not recursive unless the +@option{-r} or @option{--recursive} option is given. @command{diff} never +compares the actual contents of a directory as if it were a file. The +file that is fully specified may not be standard input, because standard +input is nameless and the notion of ``file with the same name'' does not +apply. + +If the @option{--from-file=@var{file}} option is given, the number of +file names is arbitrary, and @var{file} is compared to each named file. +Similarly, if the @option{--to-file=@var{file}} option is given, each +named file is compared to @var{file}. + +@command{diff} options begin with @samp{-}, so normally file names +may not begin with @samp{-}. However, @option{--} as an +argument by itself treats the remaining arguments as file names even if +they begin with @samp{-}. + +An exit status of 0 means no differences were found, 1 means some +differences were found, and 2 means trouble. + +@menu +* diff Options:: Summary of options to @command{diff}. +@end menu + +@node diff Options +@section Options to @command{diff} +@cindex @command{diff} options +@cindex options for @command{diff} + +Below is a summary of all of the options that @sc{gnu} @command{diff} accepts. +Most options have two equivalent names, one of which is a single letter +preceded by @samp{-}, and the other of which is a long name preceded by +@samp{--}. Multiple single letter options (unless they take an +argument) can be combined into a single command line word: @option{-ac} is +equivalent to @option{-a -c}. Long named options can be abbreviated to +any unique prefix of their name. Brackets ([ and ]) indicate that an +option takes an optional argument. + +@table @option +@item -a +@itemx --text +Treat all files as text and compare them line-by-line, even if they +do not seem to be text. @xref{Binary}. + +@item -b +@itemx --ignore-space-change +Ignore changes in amount of white space. @xref{White Space}. + +@item -B +@itemx --ignore-blank-lines +Ignore changes that just insert or delete blank lines. @xref{Blank +Lines}. + +@item --binary +Read and write data in binary mode. @xref{Binary}. + +@item -c +Use the context output format, showing three lines of context. +@xref{Context Format}. + +@item -C @var{lines} +@itemx --context@r{[}=@var{lines}@r{]} +Use the context output format, showing @var{lines} (an integer) lines of +context, or three if @var{lines} is not given. @xref{Context Format}. +For proper operation, @command{patch} typically needs at least two lines of +context. + +On older systems, @command{diff} supports an obsolete option +@option{-@var{lines}} that has effect when combined with @option{-c} +or @option{-p}. @sc{posix} 1003.1-2001 (@pxref{Standards +conformance}) does not allow this; use @option{-C @var{lines}} +instead. + +@item --changed-group-format=@var{format} +Use @var{format} to output a line group containing differing lines from +both files in if-then-else format. @xref{Line Group Formats}. + +@item -d +@itemx --minimal +Change the algorithm perhaps find a smaller set of changes. This makes +@command{diff} slower (sometimes much slower). @xref{diff Performance}. + +@item -D @var{name} +@itemx --ifdef=@var{name} +Make merged @samp{#ifdef} format output, conditional on the preprocessor +macro @var{name}. @xref{If-then-else}. + +@item -e +@itemx --ed +Make output that is a valid @command{ed} script. @xref{ed Scripts}. + +@item -E +@itemx --ignore-tab-expansion +Ignore changes due to tab expansion. +@xref{White Space}. + +@item -f +@itemx --forward-ed +Make output that looks vaguely like an @command{ed} script but has changes +in the order they appear in the file. @xref{Forward ed}. + +@item -F @var{regexp} +@itemx --show-function-line=@var{regexp} +In context and unified format, for each hunk of differences, show some +of the last preceding line that matches @var{regexp}. @xref{Specified +Headings}. + +@item --from-file=@var{file} +Compare @var{file} to each operand; @var{file} may be a directory. + +@item --help +Output a summary of usage and then exit. + +@item --horizon-lines=@var{lines} +Do not discard the last @var{lines} lines of the common prefix +and the first @var{lines} lines of the common suffix. +@xref{diff Performance}. + +@item -i +@itemx --ignore-case +Ignore changes in case; consider upper- and lower-case letters +equivalent. @xref{Case Folding}. + +@item -I @var{regexp} +@itemx --ignore-matching-lines=@var{regexp} +Ignore changes that just insert or delete lines that match @var{regexp}. +@xref{Specified Folding}. + +@item --ignore-file-name-case +Ignore case when comparing file names during recursive comparison. +@xref{Comparing Directories}. + +@item -l +@itemx --paginate +Pass the output through @command{pr} to paginate it. @xref{Pagination}. + +@item --label=@var{label} +Use @var{label} instead of the file name in the context format +(@pxref{Context Format}) and unified format (@pxref{Unified Format}) +headers. @xref{RCS}. + +@item --left-column +Print only the left column of two common lines in side by side format. +@xref{Side by Side Format}. + +@item --line-format=@var{format} +Use @var{format} to output all input lines in if-then-else format. +@xref{Line Formats}. + +@item -n +@itemx --rcs +Output @sc{rcs}-format diffs; like @option{-f} except that each command +specifies the number of lines affected. @xref{RCS}. + +@item -N +@itemx --new-file +In directory comparison, if a file is found in only one directory, +treat it as present but empty in the other directory. @xref{Comparing +Directories}. + +@item --new-group-format=@var{format} +Use @var{format} to output a group of lines taken from just the second +file in if-then-else format. @xref{Line Group Formats}. + +@item --new-line-format=@var{format} +Use @var{format} to output a line taken from just the second file in +if-then-else format. @xref{Line Formats}. + +@item --old-group-format=@var{format} +Use @var{format} to output a group of lines taken from just the first +file in if-then-else format. @xref{Line Group Formats}. + +@item --old-line-format=@var{format} +Use @var{format} to output a line taken from just the first file in +if-then-else format. @xref{Line Formats}. + +@item -p +@itemx --show-c-function +Show which C function each change is in. @xref{C Function Headings}. + +@item -q +@itemx --brief +Report only whether the files differ, not the details of the +differences. @xref{Brief}. + +@item -r +@itemx --recursive +When comparing directories, recursively compare any subdirectories +found. @xref{Comparing Directories}. + +@item -s +@itemx --report-identical-files +Report when two files are the same. @xref{Comparing Directories}. + +@item -S @var{file} +@itemx --starting-file=@var{file} +When comparing directories, start with the file @var{file}. This is +used for resuming an aborted comparison. @xref{Comparing Directories}. + +@item --speed-large-files +Use heuristics to speed handling of large files that have numerous +scattered small changes. @xref{diff Performance}. + +@item --strip-trailing-cr +Strip any trailing carriage return at the end of an input line. +@xref{Binary}. + +@item --suppress-common-lines +Do not print common lines in side by side format. +@xref{Side by Side Format}. + +@item -t +@itemx --expand-tabs +Expand tabs to spaces in the output, to preserve the alignment of tabs +in the input files. @xref{Tabs}. + +@item -T +@itemx --initial-tab +Output a tab rather than a space before the text of a line in normal or +context format. This causes the alignment of tabs in the line to look +normal. @xref{Tabs}. + +@item --to-file=@var{file} +Compare each operand to @var{file}; @var{file} may be a directory. + +@item -u +Use the unified output format, showing three lines of context. +@xref{Unified Format}. + +@item --unchanged-group-format=@var{format} +Use @var{format} to output a group of common lines taken from both files +in if-then-else format. @xref{Line Group Formats}. + +@item --unchanged-line-format=@var{format} +Use @var{format} to output a line common to both files in if-then-else +format. @xref{Line Formats}. + +@item --unidirectional-new-file +When comparing directories, if a file appears only in the second +directory of the two, treat it as present but empty in the other. +@xref{Comparing Directories}. + +@item -U @var{lines} +@itemx --unified@r{[}=@var{lines}@r{]} +Use the unified output format, showing @var{lines} (an integer) lines of +context, or three if @var{lines} is not given. @xref{Unified Format}. +For proper operation, @command{patch} typically needs at least two lines of +context. + +On older systems, @command{diff} supports an obsolete option +@option{-@var{lines}} that has effect when combined with @option{-u}. +@sc{posix} 1003.1-2001 (@pxref{Standards conformance}) does not allow +this; use @option{-U @var{lines}} instead. + +@item -v +@itemx --version +Output version information and then exit. + +@item -w +@itemx --ignore-all-space +Ignore white space when comparing lines. @xref{White Space}. + +@item -W @var{columns} +@itemx --width=@var{columns} +Output at most @var{columns} (default 130) print columns per line in +side by side format. @xref{Side by Side Format}. + +@item -x @var{pattern} +@itemx --exclude=@var{pattern} +When comparing directories, ignore files and subdirectories whose basenames +match @var{pattern}. @xref{Comparing Directories}. + +@item -X @var{file} +@itemx --exclude-from=@var{file} +When comparing directories, ignore files and subdirectories whose basenames +match any pattern contained in @var{file}. @xref{Comparing Directories}. + +@item -y +@itemx --side-by-side +Use the side by side output format. @xref{Side by Side Format}. +@end table + +@node Invoking diff3 +@chapter Invoking @command{diff3} +@cindex invoking @command{diff3} +@cindex @command{diff3} invocation + +The @command{diff3} command compares three files and outputs descriptions +of their differences. Its arguments are as follows: + +@example +diff3 @var{options}@dots{} @var{mine} @var{older} @var{yours} +@end example + +The files to compare are @var{mine}, @var{older}, and @var{yours}. +At most one of these three file names may be @file{-}, +which tells @command{diff3} to read the standard input for that file. + +An exit status of 0 means @command{diff3} was successful, 1 means some +conflicts were found, and 2 means trouble. + +@menu +* diff3 Options:: Summary of options to @command{diff3}. +@end menu + +@node diff3 Options +@section Options to @command{diff3} +@cindex @command{diff3} options +@cindex options for @command{diff3} + +Below is a summary of all of the options that @sc{gnu} @command{diff3} +accepts. Multiple single letter options (unless they take an argument) +can be combined into a single command line argument. + +@table @option +@item -a +@itemx --text +Treat all files as text and compare them line-by-line, even if they +do not appear to be text. @xref{Binary}. + +@item -A +@itemx --show-all +Incorporate all unmerged changes from @var{older} to @var{yours} into +@var{mine}, surrounding conflicts with bracket lines. +@xref{Marking Conflicts}. + +@item --diff-program=@var{program} +Use the compatible comparison program @var{program} to compare files +instead of @command{diff}. + +@item -e +@itemx --ed +Generate an @command{ed} script that incorporates all the changes from +@var{older} to @var{yours} into @var{mine}. @xref{Which Changes}. + +@item -E +@itemx --show-overlap +Like @option{-e}, except bracket lines from overlapping changes' first +and third files. +@xref{Marking Conflicts}. +With @option{-E}, an overlapping change looks like this: + +@example +<<<<<<< @var{mine} +@r{lines from @var{mine}} +======= +@r{lines from @var{yours}} +>>>>>>> @var{yours} +@end example + +@item --help +Output a summary of usage and then exit. + +@item -i +Generate @samp{w} and @samp{q} commands at the end of the @command{ed} +script for System V compatibility. This option must be combined with +one of the @option{-AeExX3} options, and may not be combined with @option{-m}. +@xref{Saving the Changed File}. + +@item -L @var{label} +@itemx --label=@var{label} +Use the label @var{label} for the brackets output by the @option{-A}, +@option{-E} and @option{-X} options. This option may be given up to three +times, one for each input file. The default labels are the names of +the input files. Thus @samp{diff3 -L X -L Y -L Z -m A B C} acts like +@samp{diff3 -m A B C}, except that the output looks like it came from +files named @samp{X}, @samp{Y} and @samp{Z} rather than from files +named @samp{A}, @samp{B} and @samp{C}. @xref{Marking Conflicts}. + +@item -m +@itemx --merge +Apply the edit script to the first file and send the result to standard +output. Unlike piping the output from @command{diff3} to @command{ed}, this +works even for binary files and incomplete lines. @option{-A} is assumed +if no edit script option is specified. @xref{Bypassing ed}. + +@item -T +@itemx --initial-tab +Output a tab rather than two spaces before the text of a line in normal format. +This causes the alignment of tabs in the line to look normal. @xref{Tabs}. + +@item -v +@itemx --version +Output version information and then exit. + +@item -x +@itemx --overlap-only +Like @option{-e}, except output only the overlapping changes. +@xref{Which Changes}. + +@item -X +Like @option{-E}, except output only the overlapping changes. +In other words, like @option{-x}, except bracket changes as in @option{-E}. +@xref{Marking Conflicts}. + +@item -3 +@itemx --easy-only +Like @option{-e}, except output only the nonoverlapping changes. +@xref{Which Changes}. +@end table + +@node Invoking patch +@chapter Invoking @command{patch} +@cindex invoking @command{patch} +@cindex @command{patch} invocation + +Normally @command{patch} is invoked like this: + +@example +patch <@var{patchfile} +@end example + +The full format for invoking @command{patch} is: + +@example +patch @var{options}@dots{} @r{[}@var{origfile} @r{[}@var{patchfile}@r{]}@r{]} +@end example + +You can also specify where to read the patch from with the @option{-i +@var{patchfile}} or @option{--input=@var{patchfile}} option. +If you do not specify @var{patchfile}, or if @var{patchfile} is +@file{-}, @command{patch} reads the patch (that is, the @command{diff} output) +from the standard input. + +If you do not specify an input file on the command line, @command{patch} +tries to intuit from the @dfn{leading text} (any text in the patch +that comes before the @command{diff} output) which file to edit. +@xref{Multiple Patches}. + +By default, @command{patch} replaces the original input file with the +patched version, possibly after renaming the original file into a +backup file (@pxref{Backup Names}, for a description of how +@command{patch} names backup files). You can also specify where to +put the output with the @option{-o @var{file}} or +@option{--output=@var{file}} option; however, do not use this option +if @var{file} is one of the input files. + +@menu +* patch Options:: Summary table of options to @command{patch}. +@end menu + +@node patch Options +@section Options to @command{patch} +@cindex @command{patch} options +@cindex options for @command{patch} + +Here is a summary of all of the options that @sc{gnu} @command{patch} +accepts. @xref{patch and Tradition}, for which of these options are +safe to use in older versions of @command{patch}. + +Multiple single-letter options that do not take an argument can be +combined into a single command line argument with only one dash. + +@table @option +@item -b +@itemx --backup +Back up the original contents of each file, even if backups would +normally not be made. @xref{Backups}. + +@item -B @var{prefix} +@itemx --prefix=@var{prefix} +Prepend @var{prefix} to backup file names. @xref{Backup Names}. + +@item --backup-if-mismatch +Back up the original contents of each file if the patch does not +exactly match the file. This is the default behavior when not +conforming to @sc{posix}. @xref{Backups}. + +@item --binary +Read and write all files in binary mode, except for standard output +and @file{/dev/tty}. This option has no effect on +@sc{posix}-conforming systems like @sc{gnu}/Linux. On systems where +this option makes a difference, the patch should be generated by +@samp{diff -a --binary}. @xref{Binary}. + +@item -c +@itemx --context +Interpret the patch file as a context diff. @xref{patch Input}. + +@item -d @var{directory} +@itemx --directory=@var{directory} +Make directory @var{directory} the current directory for interpreting +both file names in the patch file, and file names given as arguments to +other options. @xref{patch Directories}. + +@item -D @var{name} +@itemx --ifdef=@var{name} +Make merged if-then-else output using @var{name}. @xref{If-then-else}. + +@item --dry-run +Print the results of applying the patches without actually changing +any files. @xref{Dry Runs}. + +@item -e +@itemx --ed +Interpret the patch file as an @command{ed} script. @xref{patch Input}. + +@item -E +@itemx --remove-empty-files +Remove output files that are empty after the patches have been applied. +@xref{Creating and Removing}. + +@item -f +@itemx --force +Assume that the user knows exactly what he or she is doing, and do not +ask any questions. @xref{patch Messages}. + +@item -F @var{lines} +@itemx --fuzz=@var{lines} +Set the maximum fuzz factor to @var{lines}. @xref{Inexact}. + +@item -g @var{num} +@itemx --get=@var{num} +If @var{num} is positive, get input files from a revision control +system as necessary; if zero, do not get the files; if negative, ask +the user whether to get the files. @xref{Revision Control}. + +@item --help +Output a summary of usage and then exit. + +@item -i @var{patchfile} +@itemx --input=@var{patchfile} +Read the patch from @var{patchfile} rather than from standard input. +@xref{patch Options}. + +@item -l +@itemx --ignore-white-space +Let any sequence of blanks (spaces or tabs) in the patch file match +any sequence of blanks in the input file. @xref{Changed White Space}. + +@item -n +@itemx --normal +Interpret the patch file as a normal diff. @xref{patch Input}. + +@item -N +@itemx --forward +Ignore patches that @command{patch} thinks are reversed or already applied. +See also @option{-R}. @xref{Reversed Patches}. + +@item --no-backup-if-mismatch +Do not back up the original contents of files. This is the default +behavior when conforming to @sc{posix}. @xref{Backups}. + +@item -o @var{file} +@itemx --output=@var{file} +Use @var{file} as the output file name. @xref{patch Options}. + +@item -p@var{number} +@itemx --strip=@var{number} +Set the file name strip count to @var{number}. @xref{patch Directories}. + +@item --posix +Conform to @sc{posix}, as if the @env{POSIXLY_CORRECT} environment +variable had been set. @xref{patch and POSIX}. + +@item --quoting-style=@var{word} +Use style @var{word} to quote names in diagnostics, as if the +@env{QUOTING_STYLE} environment variable had been set to @var{word}. +@xref{patch Quoting Style}. + +@item -r @var{reject-file} +@itemx --reject-file=@var{reject-file} +Use @var{reject-file} as the reject file name. @xref{Reject Names}. + +@item -R +@itemx --reverse +Assume that this patch was created with the old and new files swapped. +@xref{Reversed Patches}. + +@item -s +@itemx --quiet +@itemx --silent +Work silently unless an error occurs. @xref{patch Messages}. + +@item -t +@itemx --batch +Do not ask any questions. @xref{patch Messages}. + +@item -T +@itemx --set-time +Set the modification and access times of patched files from time +stamps given in context diff headers, assuming that the context diff +headers use local time. @xref{Patching Time Stamps}. + +@item -u +@itemx --unified +Interpret the patch file as a unified diff. @xref{patch Input}. + +@item -v +@itemx --version +Output version information and then exit. + +@item -V @var{backup-style} +@itemx --version=control=@var{backup-style} +Select the naming convention for backup file names. @xref{Backup Names}. + +@item --verbose +Print more diagnostics than usual. @xref{patch Messages}. + +@item -x @var{number} +@itemx --debug=@var{number} +Set internal debugging flags. Of interest only to @command{patch} +patchers. + +@item -Y @var{prefix} +@itemx --basename-prefix=@var{prefix} +Prepend @var{prefix} to base names of backup files. @xref{Backup Names}. + +@item -z @var{suffix} +@itemx --suffix=@var{suffix} +Use @var{suffix} as the backup extension instead of @samp{.orig} or +@samp{~}. @xref{Backup Names}. + +@item -Z +@itemx --set-utc +Set the modification and access times of patched files from time +stamps given in context diff headers, assuming that the context diff +headers use @sc{utc}. @xref{Patching Time Stamps}. + +@end table + +@node Invoking sdiff +@chapter Invoking @command{sdiff} +@cindex invoking @command{sdiff} +@cindex @command{sdiff} invocation + +The @command{sdiff} command merges two files and interactively outputs the +results. Its arguments are as follows: + +@example +sdiff -o @var{outfile} @var{options}@dots{} @var{from-file} @var{to-file} +@end example + +This merges @var{from-file} with @var{to-file}, with output to @var{outfile}. +If @var{from-file} is a directory and @var{to-file} is not, @command{sdiff} +compares the file in @var{from-file} whose file name is that of @var{to-file}, +and vice versa. @var{from-file} and @var{to-file} may not both be +directories. + +@command{sdiff} options begin with @samp{-}, so normally @var{from-file} +and @var{to-file} may not begin with @samp{-}. However, @option{--} as an +argument by itself treats the remaining arguments as file names even if +they begin with @samp{-}. You may not use @file{-} as an input file. + +@command{sdiff} without @option{-o} (or @option{--output}) produces a +side-by-side difference. This usage is obsolete; use the @option{-y} +or @option{--side-by-side} option of @command{diff} instead. + +An exit status of 0 means no differences were found, 1 means some +differences were found, and 2 means trouble. + +@menu +* sdiff Options:: Summary of options to @command{diff}. +@end menu + +@node sdiff Options +@section Options to @command{sdiff} +@cindex @command{sdiff} options +@cindex options for @command{sdiff} + +Below is a summary of all of the options that @sc{gnu} @command{sdiff} accepts. +Each option has two equivalent names, one of which is a single +letter preceded by @samp{-}, and the other of which is a long name +preceded by @samp{--}. Multiple single letter options (unless they take +an argument) can be combined into a single command line argument. Long +named options can be abbreviated to any unique prefix of their name. + +@table @option +@item -a +@itemx --text +Treat all files as text and compare them line-by-line, even if they +do not appear to be text. @xref{Binary}. + +@item -b +@itemx --ignore-space-change +Ignore changes in amount of white space. @xref{White Space}. + +@item -B +@itemx --ignore-blank-lines +Ignore changes that just insert or delete blank lines. @xref{Blank +Lines}. + +@item -d +@itemx --minimal +Change the algorithm to perhaps find a smaller set of changes. This +makes @command{sdiff} slower (sometimes much slower). @xref{diff +Performance}. + +@item --diff-program=@var{program} +Use the compatible comparison program @var{program} to compare files +instead of @command{diff}. + +@item -E +@itemx --ignore-tab-expansion +Ignore changes due to tab expansion. +@xref{White Space}. + +@item --help +Output a summary of usage and then exit. + +@item -i +@itemx --ignore-case +Ignore changes in case; consider upper- and lower-case to be the same. +@xref{Case Folding}. + +@item -I @var{regexp} +@itemx --ignore-matching-lines=@var{regexp} +Ignore changes that just insert or delete lines that match @var{regexp}. +@xref{Specified Folding}. + +@item -l +@itemx --left-column +Print only the left column of two common lines. +@xref{Side by Side Format}. + +@item -o @var{file} +@itemx --output=@var{file} +Put merged output into @var{file}. This option is required for merging. + +@item -s +@itemx --suppress-common-lines +Do not print common lines. @xref{Side by Side Format}. + +@item --speed-large-files +Use heuristics to speed handling of large files that have numerous +scattered small changes. @xref{diff Performance}. + +@item --strip-trailing-cr +Strip any trailing carriage return at the end of an input line. +@xref{Binary}. + +@item -t +@itemx --expand-tabs +Expand tabs to spaces in the output, to preserve the alignment of tabs +in the input files. @xref{Tabs}. + +@item -v +@itemx --version +Output version information and then exit. + +@item -w @var{columns} +@itemx --width=@var{columns} +Output at most @var{columns} (default 130) print columns per line. +@xref{Side by Side Format}. Note that for historical reasons, this +option is @option{-W} in @command{diff}, @option{-w} in @command{sdiff}. + +@item -W +@itemx --ignore-all-space +Ignore white space when comparing lines. @xref{White Space}. +Note that for historical reasons, this option is @option{-w} in @command{diff}, +@option{-W} in @command{sdiff}. +@end table + +@node Standards conformance +@chapter Standards conformance +@cindex @sc{posix} + +@vindex POSIXLY_CORRECT +In a few cases, the @sc{gnu} utilities' default behavior is +incompatible with the @sc{posix} standard. To suppress these +incompatibilities, define the @env{POSIXLY_CORRECT} environment +variable. Unless you are checking for @sc{posix} conformance, you +probably do not need to define @env{POSIXLY_CORRECT}. + +Normally options and operands can appear in any order, and programs act +as if all the options appear before any operands. For example, +@samp{diff lao tzu -C 2} acts like @samp{diff -C 2 lao tzu}, since +@samp{2} is an option-argument of @option{-C}. However, if the +@env{POSIXLY_CORRECT} environment variable is set, options must appear +before operands, unless otherwise specified for a particular command. + +Newer versions of @sc{posix} are occasionally incompatible with older +versions. For example, older versions of @sc{posix} allowed the +command @samp{diff -c -10} to have the same meaning as @samp{diff -C +10}, but @sc{posix} 1003.1-2001 @samp{diff} no longer allows +digit-string options like @option{-10}. + +@vindex _POSIX2_VERSION +The @sc{gnu} utilities normally conform to the version of @sc{posix} +that is standard for your system. To cause them to conform to a +different version of @sc{posix}, define the @env{_POSIX2_VERSION} +environment variable to a value of the form @var{yyyymm} specifying +the year and month the standard was adopted. Two values are currently +supported for @env{_POSIX2_VERSION}: @samp{199209} stands for +@sc{posix} 1003.2-1992, and @samp{200112} stands for @sc{posix} +1003.1-2001. For example, if you are running older software that +assumes an older version of @sc{posix} and uses @samp{diff -c -10}, +you can work around the compatibility problems by setting +@samp{_POSIX2_VERSION=199209} in your environment. + +@node Projects +@chapter Future Projects + +Here are some ideas for improving @sc{gnu} @command{diff} and +@command{patch}. The @sc{gnu} project has identified some +improvements as potential programming projects for volunteers. You +can also help by reporting any bugs that you find. + +If you are a programmer and would like to contribute something to the +@sc{gnu} project, please consider volunteering for one of these +projects. If you are seriously contemplating work, please write to +@email{gnu@@gnu.org} to coordinate with other volunteers. + +@menu +* Shortcomings:: Suggested projects for improvements. +* Bugs:: Reporting bugs. +@end menu + +@node Shortcomings +@section Suggested Projects for Improving @sc{gnu} @command{diff} and @command{patch} +@cindex projects for directories + +One should be able to use @sc{gnu} @command{diff} to generate a patch from any +pair of directory trees, and given the patch and a copy of one such +tree, use @command{patch} to generate a faithful copy of the other. +Unfortunately, some changes to directory trees cannot be expressed using +current patch formats; also, @command{patch} does not handle some of the +existing formats. These shortcomings motivate the following suggested +projects. + +@menu +* Internationalization:: Handling multibyte and varying-width characters. +* Changing Structure:: Handling changes to the directory structure. +* Special Files:: Handling symbolic links, device special files, etc. +* Unusual File Names:: Handling file names that contain unusual characters. +* Time Stamp Order:: Outputting diffs in time stamp order. +* Ignoring Changes:: Ignoring certain changes while showing others. +* Speedups:: Improving performance. +@end menu + +@node Internationalization +@subsection Handling Multibyte and Varying-Width Characters +@cindex multibyte characters +@cindex varying-width characters + +@command{diff}, @command{diff3} and @command{sdiff} treat each line of +input as a string of unibyte characters. This can mishandle multibyte +characters in some cases. For example, when asked to ignore spaces, +@command{diff} does not properly ignore a multibyte space character. + +Also, @command{diff} currently assumes that each byte is one column +wide, and this assumption is incorrect in some locales, e.g., locales +that use UTF-8 encoding. This causes problems with the @option{-y} or +@option{--side-by-side} option of @command{diff}. + +These problems need to be fixed without unduly affecting the +performance of the utilities in unibyte environments. + +The IBM GNU/Linux Technology Center Internationalization Team has +proposed some patches to support internationalized @command{diff} +@uref{http://oss.software.ibm.com/developer/opensource/linux/patches/i18n/diffutils-2.7.2-i18n-0.1.patch.gz}. +Unfortunately, these patches are incomplete and are to an older +version of @command{diff}, so more work needs to be done in this area. + +@node Changing Structure +@subsection Handling Changes to the Directory Structure +@cindex directory structure changes + +@command{diff} and @command{patch} do not handle some changes to directory +structure. For example, suppose one directory tree contains a directory +named @samp{D} with some subsidiary files, and another contains a file +with the same name @samp{D}. @samp{diff -r} does not output enough +information for @command{patch} to transform the directory subtree into +the file. + +There should be a way to specify that a file has been removed without +having to include its entire contents in the patch file. There should +also be a way to tell @command{patch} that a file was renamed, even if +there is no way for @command{diff} to generate such information. +There should be a way to tell @command{patch} that a file's time stamp +has changed, even if its contents have not changed. + +These problems can be fixed by extending the @command{diff} output format +to represent changes in directory structure, and extending @command{patch} +to understand these extensions. + +@node Special Files +@subsection Files that are Neither Directories Nor Regular Files +@cindex special files + +Some files are neither directories nor regular files: they are unusual +files like symbolic links, device special files, named pipes, and +sockets. Currently, @command{diff} treats symbolic links like regular files; +it treats other special files like regular files if they are specified +at the top level, but simply reports their presence when comparing +directories. This means that @command{patch} cannot represent changes +to such files. For example, if you change which file a symbolic link +points to, @command{diff} outputs the difference between the two files, +instead of the change to the symbolic link. + +@c This might not be a good idea; is it wise for root to install devices +@c this way? +@command{diff} should optionally report changes to special files specially, +and @command{patch} should be extended to understand these extensions. + +@node Unusual File Names +@subsection File Names that Contain Unusual Characters +@cindex file names with unusual characters + +When a file name contains an unusual character like a newline or +white space, @samp{diff -r} generates a patch that @command{patch} cannot +parse. The problem is with format of @command{diff} output, not just with +@command{patch}, because with odd enough file names one can cause +@command{diff} to generate a patch that is syntactically correct but +patches the wrong files. The format of @command{diff} output should be +extended to handle all possible file names. + +@node Time Stamp Order +@subsection Outputting Diffs in Time Stamp Order + +Applying @command{patch} to a multiple-file diff can result in files +whose time stamps are out of order. @sc{gnu} @command{patch} has +options to restore the time stamps of the updated files +(@pxref{Patching Time Stamps}), but sometimes it is useful to generate +a patch that works even if the recipient does not have @sc{gnu} patch, +or does not use these options. One way to do this would be to +implement a @command{diff} option to output diffs in time stamp order. + +@node Ignoring Changes +@subsection Ignoring Certain Changes + +It would be nice to have a feature for specifying two strings, one in +@var{from-file} and one in @var{to-file}, which should be considered to +match. Thus, if the two strings are @samp{foo} and @samp{bar}, then if +two lines differ only in that @samp{foo} in file 1 corresponds to +@samp{bar} in file 2, the lines are treated as identical. + +It is not clear how general this feature can or should be, or +what syntax should be used for it. + +A partial substitute is to filter one or both files before comparing, +e.g.: + +@example +sed 's/foo/bar/g' file1 | diff - file2 +@end example + +However, this outputs the filtered text, not the original. + +@node Speedups +@subsection Improving Performance + +When comparing two large directory structures, one of which was +originally copied from the other with time stamps preserved (e.g., +with @samp{cp -pR}), it would greatly improve performance if an option +told @command{diff} to assume that two files with the same size and +time stamps have the same content. @xref{diff Performance}. + +@node Bugs +@section Reporting Bugs +@cindex bug reports +@cindex reporting bugs + +If you think you have found a bug in @sc{gnu} @command{cmp}, +@command{diff}, @command{diff3}, or @command{sdiff}, please report it +by electronic mail to the +@uref{http://mail.gnu.org/mailman/listinfo/bug-gnu-utils,GNU utilities +bug report mailing list} @email{bug-gnu-utils@@gnu.org}. Please send +bug reports for @sc{gnu} @command{patch} to +@email{bug-patch@@gnu.org}. Send as precise a description of the +problem as you can, including the output of the @option{--version} +option and sample input files that produce the bug, if applicable. If +you have a nontrivial fix for the bug, please send it as well. If you +have a patch, please send it too. It may simplify the maintainer's +job if the patch is relative to a recent test release, which you can +find in the directory @uref{ftp://alpha.gnu.org/gnu/diffutils/}. + +@node Copying This Manual +@appendix Copying This Manual + +@menu +* GNU Free Documentation License:: License for copying this manual. +@end menu + +@include fdl.texi + +@node Index +@appendix Index + +@printindex cp + +@bye diff --git a/external/gpl2/diffutils/dist/doc/fdl.texi b/external/gpl2/diffutils/dist/doc/fdl.texi new file mode 100644 index 00000000000..0c30df24036 --- /dev/null +++ b/external/gpl2/diffutils/dist/doc/fdl.texi @@ -0,0 +1,404 @@ + +@c $NetBSD: fdl.texi,v 1.1.1.1 2016/01/13 03:15:29 christos Exp $ +@node GNU Free Documentation License +@appendixsec GNU Free Documentation License + +@cindex FDL, GNU Free Documentation License +@center Version 1.1, March 2000 + +@display +Copyright @copyright{} 2000 Free Software Foundation, Inc. +59 Temple Place, Suite 330, Boston, MA 02111-1307, USA + +Everyone is permitted to copy and distribute verbatim copies +of this license document, but changing it is not allowed. +@end display + +@enumerate 0 +@item +PREAMBLE + +The purpose of this License is to make a manual, textbook, or other +written document @dfn{free} in the sense of freedom: to assure everyone +the effective freedom to copy and redistribute it, with or without +modifying it, either commercially or noncommercially. Secondarily, +this License preserves for the author and publisher a way to get +credit for their work, while not being considered responsible for +modifications made by others. + +This License is a kind of ``copyleft'', which means that derivative +works of the document must themselves be free in the same sense. It +complements the GNU General Public License, which is a copyleft +license designed for free software. + +We have designed this License in order to use it for manuals for free +software, because free software needs free documentation: a free +program should come with manuals providing the same freedoms that the +software does. But this License is not limited to software manuals; +it can be used for any textual work, regardless of subject matter or +whether it is published as a printed book. We recommend this License +principally for works whose purpose is instruction or reference. + +@item +APPLICABILITY AND DEFINITIONS + +This License applies to any manual or other work that contains a +notice placed by the copyright holder saying it can be distributed +under the terms of this License. The ``Document'', below, refers to any +such manual or work. Any member of the public is a licensee, and is +addressed as ``you''. + +A ``Modified Version'' of the Document means any work containing the +Document or a portion of it, either copied verbatim, or with +modifications and/or translated into another language. + +A ``Secondary Section'' is a named appendix or a front-matter section of +the Document that deals exclusively with the relationship of the +publishers or authors of the Document to the Document's overall subject +(or to related matters) and contains nothing that could fall directly +within that overall subject. (For example, if the Document is in part a +textbook of mathematics, a Secondary Section may not explain any +mathematics.) 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You must delete all sections +entitled ``Endorsements.'' + +@item +COLLECTIONS OF DOCUMENTS + +You may make a collection consisting of the Document and other documents +released under this License, and replace the individual copies of this +License in the various documents with a single copy that is included in +the collection, provided that you follow the rules of this License for +verbatim copying of each of the documents in all other respects. + +You may extract a single document from such a collection, and distribute +it individually under this License, provided you insert a copy of this +License into the extracted document, and follow this License in all +other respects regarding verbatim copying of that document. + +@item +AGGREGATION WITH INDEPENDENT WORKS + +A compilation of the Document or its derivatives with other separate +and independent documents or works, in or on a volume of a storage or +distribution medium, does not as a whole count as a Modified Version +of the Document, provided no compilation copyright is claimed for the +compilation. Such a compilation is called an ``aggregate'', and this +License does not apply to the other self-contained works thus compiled +with the Document, on account of their being thus compiled, if they +are not themselves derivative works of the Document. + +If the Cover Text requirement of section 3 is applicable to these +copies of the Document, then if the Document is less than one quarter +of the entire aggregate, the Document's Cover Texts may be placed on +covers that surround only the Document within the aggregate. +Otherwise they must appear on covers around the whole aggregate. + +@item +TRANSLATION + +Translation is considered a kind of modification, so you may +distribute translations of the Document under the terms of section 4. +Replacing Invariant Sections with translations requires special +permission from their copyright holders, but you may include +translations of some or all Invariant Sections in addition to the +original versions of these Invariant Sections. You may include a +translation of this License provided that you also include the +original English version of this License. In case of a disagreement +between the translation and the original English version of this +License, the original English version will prevail. + +@item +TERMINATION + +You may not copy, modify, sublicense, or distribute the Document except +as expressly provided for under this License. Any other attempt to +copy, modify, sublicense or distribute the Document is void, and will +automatically terminate your rights under this License. However, +parties who have received copies, or rights, from you under this +License will not have their licenses terminated so long as such +parties remain in full compliance. + +@item +FUTURE REVISIONS OF THIS LICENSE + +The Free Software Foundation may publish new, revised versions +of the GNU Free Documentation License from time to time. Such new +versions will be similar in spirit to the present version, but may +differ in detail to address new problems or concerns. See +@uref{http://www.gnu.org/copyleft/}. + +Each version of the License is given a distinguishing version number. +If the Document specifies that a particular numbered version of this +License ``or any later version'' applies to it, you have the option of +following the terms and conditions either of that specified version or +of any later version that has been published (not as a draft) by the +Free Software Foundation. If the Document does not specify a version +number of this License, you may choose any version ever published (not +as a draft) by the Free Software Foundation. +@end enumerate + +@page +@appendixsubsec ADDENDUM: How to use this License for your documents + +To use this License in a document you have written, include a copy of +the License in the document and put the following copyright and +license notices just after the title page: + +@smallexample +@group + Copyright (C) @var{year} @var{your name}. + Permission is granted to copy, distribute and/or modify this document + under the terms of the GNU Free Documentation License, Version 1.1 + or any later version published by the Free Software Foundation; + with the Invariant Sections being @var{list their titles}, with the + Front-Cover Texts being @var{list}, and with the Back-Cover Texts being @var{list}. + A copy of the license is included in the section entitled ``GNU + Free Documentation License''. +@end group +@end smallexample + +If you have no Invariant Sections, write ``with no Invariant Sections'' +instead of saying which ones are invariant. If you have no +Front-Cover Texts, write ``no Front-Cover Texts'' instead of +``Front-Cover Texts being @var{list}''; likewise for Back-Cover Texts. + +If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, +to permit their use in free software. + +@c Local Variables: +@c ispell-local-pdict: "ispell-dict" +@c End: + diff --git a/external/gpl2/diffutils/dist/doc/stamp-vti b/external/gpl2/diffutils/dist/doc/stamp-vti new file mode 100644 index 00000000000..5e7a10cf720 --- /dev/null +++ b/external/gpl2/diffutils/dist/doc/stamp-vti @@ -0,0 +1,4 @@ +@set UPDATED 5 April 2002 +@set UPDATED-MONTH April 2002 +@set EDITION 2.8.1 +@set VERSION 2.8.1 diff --git a/external/gpl2/diffutils/dist/doc/version.texi b/external/gpl2/diffutils/dist/doc/version.texi new file mode 100644 index 00000000000..430bceb5ba7 --- /dev/null +++ b/external/gpl2/diffutils/dist/doc/version.texi @@ -0,0 +1,5 @@ +@set UPDATED 5 April 2002 +@c $NetBSD: version.texi,v 1.1.1.1 2016/01/13 03:15:29 christos Exp $ +@set UPDATED-MONTH April 2002 +@set EDITION 2.8.1 +@set VERSION 2.8.1 |
