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diff --git a/doc/diffutils.info b/doc/diffutils.info new file mode 100644 index 0000000..179f11d --- /dev/null +++ b/doc/diffutils.info @@ -0,0 +1,5313 @@ +This is diffutils.info-t, produced by makeinfo version 6.1 from +diffutils.texi. + +This manual is for GNU Diffutils (version 3.5, 4 August 2016), 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) 1992-1994, 1998, 2001-2002, 2004, 2006, 2009-2016 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 1.3 or any later version published by the Free Software + Foundation; with no Invariant Sections, no Front-Cover Texts, and + no Back-Cover Texts. A copy of the license is included in the + section entitled "GNU Free Documentation License." +INFO-DIR-SECTION Individual utilities +START-INFO-DIR-ENTRY +* cmp: (diffutils)Invoking cmp. Compare 2 files byte by byte. +* diff: (diffutils)Invoking diff. Compare 2 files line by line. +* diff3: (diffutils)Invoking diff3. Compare 3 files line by line. +* patch: (diffutils)Invoking patch. Apply a patch to a file. +* sdiff: (diffutils)Invoking sdiff. Merge 2 files side-by-side. +END-INFO-DIR-ENTRY + +INFO-DIR-SECTION Text creation and manipulation +START-INFO-DIR-ENTRY +* Diffutils: (diffutils). Comparing and merging files. +END-INFO-DIR-ENTRY + + +File: diffutils.info-t, Node: Top, Next: Overview, Up: (dir) + +Comparing and Merging Files +*************************** + +This manual is for GNU Diffutils (version 3.5, 4 August 2016), 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) 1992-1994, 1998, 2001-2002, 2004, 2006, 2009-2016 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 1.3 or any later version published by the Free Software + Foundation; with no Invariant Sections, no Front-Cover Texts, and + no Back-Cover Texts. A copy of the license is included in the + section entitled "GNU Free Documentation License." + +* 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. +* Translations:: Available translations of this manual. +* Index:: Index. + + +File: diffutils.info-t, 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 by Eugene +W. Myers in "An O(ND) Difference Algorithm and its Variations", +'Algorithmica' Vol. 1, 1986, pp. 251-266, +<http://dx.doi.org/10.1007/BF01840446>; and in "A File Comparison +Program", Webb Miller and Eugene W. Myers, 'Software--Practice and +Experience' Vol. 15, 1985, pp. 1025-1040, +<http://dx.doi.org/10.1002/spe.4380151102>. The algorithm was +independently discovered as described by Esko Ukkonen in "Algorithms for +Approximate String Matching", 'Information and Control' Vol. 64, 1985, +pp. 100-118, <http://dx.doi.org/10.1016/S0019-9958(85)80046-2>. Related +algorithms are surveyed by Alfred V. Aho in section 6.3 of "Algorithms +for Finding Patterns in Strings", 'Handbook of Theoretical Computer +Science' (Jan Van Leeuwen, ed.), Vol. A, 'Algorithms and Complexity', +Elsevier/MIT Press, 1990, pp. 255-300. + + GNU 'diff3' was written by Randy Smith. GNU 'sdiff' was written by +Thomas Lord. GNU 'cmp' was written by Torbjo"rn Granlund and David +MacKenzie. + + GNU '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: diffutils.info-t, Node: Comparison, Next: Output Formats, Prev: Overview, Up: Top + +1 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. + + These commands compare input files without necessarily reading them. +For example, if 'diff' is asked simply to report whether two files +differ, and it discovers that the files have different sizes, it need +not read them to do its job. + +* Menu: + +* Hunks:: Groups of differing lines. +* White Space:: Suppressing differences in white space. +* Blank Lines:: Suppressing differences whose lines are all blank. +* Specified Lines:: Suppressing differences whose lines all match a pattern. +* Case Folding:: Suppressing differences in alphabetic case. +* Brief:: Summarizing which files are different. +* Binary:: Comparing binary files or forcing text comparisons. + + +File: diffutils.info-t, Node: Hunks, Next: White Space, Up: Comparison + +1.1 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' ('-d') option (*note +diff Performance::). + + +File: diffutils.info-t, Node: White Space, Next: Blank Lines, Prev: Hunks, Up: Comparison + +1.2 Suppressing Differences in Blank and Tab Spacing +==================================================== + +The '--ignore-tab-expansion' ('-E') option ignores 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 (*note Tabs::). + + The '--ignore-trailing-space' ('-Z') option ignores white space at +line end. + + The '--ignore-space-change' ('-b') option is stronger than '-E' and +'-Z' combined. It ignores white space at line end, and considers all +other sequences of one or more white space characters within a line to +be equivalent. With this option, '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 '--ignore-all-space' ('-w') option is stronger still. It ignores +differences even if one line has white space where the other line has +none. "White space" characters include tab, vertical tab, form feed, +carriage return, and space; some locales may define additional +characters to be white space. With this option, '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$ + + For many other programs newline is also a white space character, but +'diff' is a line-oriented program and a newline character always ends a +line. Hence the '-w' or '--ignore-all-space' option does not ignore +newline-related changes; it ignores only other white space changes. + + +File: diffutils.info-t, Node: Blank Lines, Next: Specified Lines, Prev: White Space, Up: Comparison + +1.3 Suppressing Differences Whose Lines Are All Blank +===================================================== + +The '--ignore-blank-lines' ('-B') option ignores changes that consist +entirely of blank lines. With this option, 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 + + Normally this option affects only lines that are completely empty, +but if you also specify an option that ignores trailing spaces, lines +are also affected if they look empty but contain white space. In other +words, '-B' is equivalent to '-I '^$'' by default, but it is equivalent +to '-I '^[[:space:]]*$'' if '-b', '-w' or '-Z' is also specified. + + +File: diffutils.info-t, Node: Specified Lines, Next: Case Folding, Prev: Blank Lines, Up: Comparison + +1.4 Suppressing Differences Whose Lines All Match a Regular Expression +====================================================================== + +To ignore insertions and deletions of lines that match a 'grep'-style +regular expression, use the '--ignore-matching-lines=REGEXP' ('-I +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: diffutils.info-t, Node: Case Folding, Next: Brief, Prev: Specified Lines, Up: Comparison + +1.5 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: diffutils.info-t, Node: Brief, Next: Binary, Prev: Case Folding, Up: Comparison + +1.6 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 '--brief' ('-q') +option selects 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, or reports that one file is a +prefix of the other. You can use the '-s', '--quiet', or '--silent' +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: diffutils.info-t, Node: Binary, Prev: Brief, Up: Comparison + +1.7 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. This does not +count as trouble, even though the resulting output does not capture all +the differences. + + '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 '--text' ('-a') +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 report only whether files differ (but +not how). Use the '--brief' ('-q') option for this. + + 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 '--verbose' ('-l') option to show the values of each +differing byte in the two files. With GNU 'cmp', you can also use the +'-b' or '--print-bytes' 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' option. + + +File: diffutils.info-t, Node: Output Formats, Next: Incomplete Lines, Prev: Comparison, Up: Top + +2 '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. +* Context:: Showing differences with the surrounding text. +* Side by Side:: Showing differences in two columns. +* Normal:: Showing differences without surrounding text. +* Scripts:: Generating scripts for other programs. +* If-then-else:: Merging files with if-then-else. + + +File: diffutils.info-t, Node: Sample diff Input, Next: Context, Up: Output Formats + +2.1 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: diffutils.info-t, Node: Context, Next: Side by Side, Prev: Sample diff Input, Up: Output Formats + +2.2 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: diffutils.info-t, Node: Context Format, Next: Unified Format, Up: Context + +2.2.1 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 '--context[=LINES]' ('-C +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: + +* Example Context:: Sample output in context format. +* Less Context:: Another sample with less context. +* Detailed Context:: A detailed description of the context output format. + + +File: diffutils.info-t, Node: Example Context, Next: Less Context, Up: Context Format + +2.2.1.1 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: diffutils.info-t, Node: Less Context, Next: Detailed Context, Prev: Example Context, Up: Context Format + +2.2.1.2 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: diffutils.info-t, Node: Detailed Context, Prev: Less Context, Up: Context Format + +2.2.1.3 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). (The +fractional seconds are omitted on hosts that do not support fractional +time stamps.) 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-NUMBERS **** + FROM-FILE-LINE + FROM-FILE-LINE... + --- TO-FILE-LINE-NUMBERS ---- + TO-FILE-LINE + TO-FILE-LINE... + + If a hunk contains two or more lines, its line numbers look like +'START,END'. Otherwise only its end line number appears. An empty hunk +is considered to end at the line that precedes the hunk. + + 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: diffutils.info-t, Node: Unified Format, Next: Sections, Prev: Context Format, Up: Context + +2.2.2 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 '--unified[=LINES]' ('-U 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: + +* Example Unified:: Sample output in unified format. +* Detailed Unified:: A detailed description of unified format. + + +File: diffutils.info-t, Node: Example Unified, Next: Detailed Unified, Up: Unified Format + +2.2.2.1 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: diffutils.info-t, Node: Detailed Unified, Prev: Example Unified, Up: Unified Format + +2.2.2.2 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. The +fractional seconds are omitted on hosts that do not support fractional +time stamps. + + You can change the header's content with the '--label=LABEL' option. +*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-LINE-NUMBERS TO-FILE-LINE-NUMBERS @@ + LINE-FROM-EITHER-FILE + LINE-FROM-EITHER-FILE... + + If a hunk contains just one line, only its start line number appears. +Otherwise its line numbers look like 'START,COUNT'. An empty hunk is +considered to start at the line that follows the hunk. + + If a hunk and its context contain two or more lines, its line numbers +look like 'START,COUNT'. Otherwise only its end line number appears. +An empty hunk is considered to end at the line that precedes the hunk. + + 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: diffutils.info-t, Node: Sections, Next: Alternate Names, Prev: Unified Format, Up: Context + +2.2.3 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: diffutils.info-t, Node: Specified Headings, Next: C Function Headings, Up: Sections + +2.2.3.1 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 +'--show-function-line=REGEXP' ('-F 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:]$_]' + C, C++, Prolog +'^(' + Lisp +'^@node' + Texinfo + + This option does not automatically select an output format; in order +to use it, you must select the context format (*note Context Format::) +or unified format (*note Unified Format::). In other output formats it +has no effect. + + The '--show-function-line' ('-F') option finds the nearest unchanged +line that precedes each hunk of differences and matches the given +regular expression. Then it adds that line to the end of the line of +asterisks in the context format, or to the '@@' line in unified format. +If no matching line exists, this option leaves the output for that hunk +unchanged. If that line is more than 40 characters long, it outputs +only the first 40 characters. You can specify more than one regular +expression for such lines; 'diff' tries to match each line against each +regular expression, starting with the last one given. This means that +you can use '-p' and '-F' together, if you wish. + + +File: diffutils.info-t, Node: C Function Headings, Prev: Specified Headings, Up: Sections + +2.2.3.2 Showing C Function Headings +................................... + +To show in which functions differences occur for C and similar +languages, you can use the '--show-c-function' ('-p') option. This +option automatically defaults to the context output format (*note +Context Format::), with the default number of lines of context. You can +override that number with '-C LINES' elsewhere in the command line. You +can override both the format and the number with '-U LINES' elsewhere in +the command line. + + The '--show-c-function' ('-p') option is equivalent to '-F +'^[[:alpha:]$_]'' if the unified format is specified, otherwise '-c -F +'^[[:alpha:]$_]'' (*note Specified Headings::). GNU 'diff' provides +this option for the sake of convenience. + + +File: diffutils.info-t, Node: Alternate Names, Prev: Sections, Up: Context + +2.2.4 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: diffutils.info-t, Node: Side by Side, Next: Normal, Prev: Context, Up: Output Formats + +2.3 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: diffutils.info-t, Node: Side by Side Format, Next: Example Side by Side, Up: Side by Side + +2.3.1 Controlling Side by Side Format +------------------------------------- + +The '--side-by-side' ('-y') 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 +'--width=COLUMNS' ('-W 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: diffutils.info-t, Node: Example Side by Side, Prev: Side by Side Format, Up: Side by Side + +2.3.2 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: diffutils.info-t, Node: Normal, Next: Scripts, Prev: Side by Side, Up: Output Formats + +2.4 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: + +* Example Normal:: Sample output in the normal format. +* Detailed Normal:: A detailed description of normal output format. + + +File: diffutils.info-t, Node: Example Normal, Next: Detailed Normal, Up: Normal + +2.4.1 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: diffutils.info-t, Node: Detailed Normal, Prev: Example Normal, Up: Normal + +2.4.2 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: diffutils.info-t, Node: Scripts, Next: If-then-else, Prev: Normal, Up: Output Formats + +2.5 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: diffutils.info-t, Node: ed Scripts, Next: Forward ed, Up: Scripts + +2.5.1 '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 '--ed' ('-e') +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: + +* Example ed:: A sample 'ed' script. +* Detailed ed:: A detailed description of 'ed' format. + + +File: diffutils.info-t, Node: Example ed, Next: Detailed ed, Up: ed Scripts + +2.5.1.1 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: diffutils.info-t, Node: Detailed ed, Prev: Example ed, Up: ed Scripts + +2.5.1.2 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: diffutils.info-t, Node: Forward ed, Next: RCS, Prev: ed Scripts, Up: Scripts + +2.5.2 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: diffutils.info-t, Node: RCS, Prev: Forward ed, Up: Scripts + +2.5.3 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 '--rcs' ('-n') 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: diffutils.info-t, Node: If-then-else, Prev: Scripts, Up: Output Formats + +2.6 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. +* Example If-then-else:: Sample if-then-else format output. +* Detailed If-then-else:: A detailed description of if-then-else format. + + +File: diffutils.info-t, Node: Line Group Formats, Next: Line Formats, Up: If-then-else + +2.6.1 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 new file) is + 0, to '1 line' if N is 1, and to '%dN lines' otherwise. + + +File: diffutils.info-t, Node: Line Formats, Next: Example If-then-else, Prev: Line Group Formats, Up: If-then-else + +2.6.2 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: diffutils.info-t, Node: Example If-then-else, Next: Detailed If-then-else, Prev: Line Formats, Up: If-then-else + +2.6.3 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: diffutils.info-t, Node: Detailed If-then-else, Prev: Example If-then-else, Up: If-then-else + +2.6.4 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: diffutils.info-t, Node: Incomplete Lines, Next: Comparing Directories, Prev: Output Formats, Up: Top + +3 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: diffutils.info-t, Node: Comparing Directories, Next: Adjusting Output, Prev: Incomplete Lines, Up: Top + +4 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 '--report-identical-files' ('-s') +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. + + If only one file exists, 'diff' normally does not show its contents; +it merely reports that one file exists but the other does not. You can +make 'diff' act as though the missing file is empty, 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 the missing file +is in the first or the second position.) To do this, use the +'--new-file' ('-N') option. This option affects command-line arguments +as well as files found via directory traversal; for example, 'diff -N a +b' treats 'a' as empty if 'a' does not exist but 'b' does, and similarly +'diff -N - b' treats standard input as empty if it is closed but 'b' +exists. + + If the older directory contains 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 inserts the contents only 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 +'--exclude=PATTERN' ('-x 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 +'--exclude-from=FILE' ('-X FILE') option. Trailing white space and +empty lines are ignored in the pattern file. + + 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 '--starting-file=FILE' ('-S 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 '--exclude=PATTERN' ('-x PATTERN') option, or an +'--exclude-from=FILE' ('-X 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. + + To tell 'diff' not to follow a symbolic link, use the +'--no-dereference' option. + + +File: diffutils.info-t, Node: Adjusting Output, Next: diff Performance, Prev: Comparing Directories, Up: Top + +5 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. +* Trailing Blanks:: Suppressing blanks before empty output lines. +* Pagination:: Page numbering and time-stamping 'diff' output. + + +File: diffutils.info-t, Node: Tabs, Next: Trailing Blanks, Up: Adjusting Output + +5.1 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 +'--expand-tabs' ('-t') option. 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). 'diff' normally assumes +that tab stops are set every 8 print columns, but this can be altered by +the '--tabsize=COLUMNS' option. + + 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: diffutils.info-t, Node: Trailing Blanks, Next: Pagination, Prev: Tabs, Up: Adjusting Output + +5.2 Omitting trailing blanks +============================ + +When outputting lines in normal or context format, or outputting an +unchanged line in unified format, 'diff' normally outputs a blank just +before each line. If the line is empty, the output of 'diff' therefore +contains trailing blanks even though the input does not contain them. +For example, when outputting an unchanged empty line in context format, +'diff' normally outputs a line with two leading spaces. + + Some text editors and email agents routinely delete trailing blanks, +so it can be a problem to deal with diff output files that contain them. +You can avoid this problem with the '--suppress-blank-empty' option. It +causes 'diff' to omit trailing blanks at the end of output lines in +normal, context, and unified format, unless the trailing blanks were +already present in the input. This changes the output format slightly, +so that output lines are guaranteed to never end in a blank unless an +input line ends in a blank. This format is less likely to be munged by +text editors or by transmission via email. It is accepted by GNU +'patch' as well. + + +File: diffutils.info-t, Node: Pagination, Prev: Trailing Blanks, Up: Adjusting Output + +5.3 Paginating 'diff' Output +============================ + +It can be convenient to have long output page-numbered and time-stamped. +The '--paginate' ('-l') option does 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: diffutils.info-t, Node: diff Performance, Next: Comparing Three Files, Prev: Adjusting Output, Up: Top + +6 '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 '--minimal' ('-d') 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: diffutils.info-t, Node: Comparing Three Files, Next: diff3 Merging, Prev: diff Performance, Up: Top + +7 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. +* Example diff3 Normal:: Sample output in the normal format. +* Detailed diff3 Normal:: A detailed description of normal output format. +* diff3 Hunks:: The format of normal output format. + + +File: diffutils.info-t, Node: Sample diff3 Input, Next: Example diff3 Normal, Up: Comparing Three Files + +7.1 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: diffutils.info-t, Node: Example diff3 Normal, Next: Detailed diff3 Normal, Prev: Sample diff3 Input, Up: Comparing Three Files + +7.2 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: diffutils.info-t, Node: Detailed diff3 Normal, Next: diff3 Hunks, Prev: Example diff3 Normal, Up: Comparing Three Files + +7.3 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 '--initial-tab' ('-T') +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 there is only one line. 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: diffutils.info-t, Node: diff3 Hunks, Prev: Detailed diff3 Normal, Up: Comparing Three Files + +7.4 '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: diffutils.info-t, Node: diff3 Merging, Next: Interactive Merging, Prev: Comparing Three Files, Up: Top + +8 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: diffutils.info-t, Node: Which Changes, Next: Marking Conflicts, Up: diff3 Merging + +8.1 Selecting Which Changes to Incorporate +========================================== + +You can select all unmerged changes from OLDER to YOURS for merging into +MINE with the '--ed' ('-e') option. You can select only the +nonoverlapping unmerged changes with '--easy-only' ('-3'), and you can +select only the overlapping changes with '--overlap-only' ('-x'). + + 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 '--show-all' ('-A') 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: diffutils.info-t, Node: Marking Conflicts, Next: Bypassing ed, Prev: Which Changes, Up: diff3 Merging + +8.2 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 '--show-all' ('-A') 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 '--show-overlap' ('-E') option outputs less information than the +'--show-all' ('-A') 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 '--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 +--label X --label Y --label 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: diffutils.info-t, Node: Bypassing ed, Next: Merging Incomplete Lines, Prev: Marking Conflicts, Up: diff3 Merging + +8.3 Generating the Merged Output Directly +========================================= + +With the '--merge' ('-m') 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' 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: diffutils.info-t, Node: Merging Incomplete Lines, Next: Saving the Changed File, Prev: Bypassing ed, Up: diff3 Merging + +8.4 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: diffutils.info-t, Node: Saving the Changed File, Prev: Merging Incomplete Lines, Up: diff3 Merging + +8.5 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: diffutils.info-t, Node: Interactive Merging, Next: Merging with patch, Prev: diff3 Merging, Up: Top + +9 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 +'--output=FILE' ('-o 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: diffutils.info-t, Node: sdiff Option Summary, Next: Merge Commands, Up: Interactive Merging + +9.1 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 -Z + + --expand-tabs + --ignore-blank-lines --ignore-case + --ignore-matching-lines=REGEXP --ignore-space-change + --ignore-tab-expansion --ignore-trailing-space + --left-column --minimal --speed-large-files + --strip-trailing-cr --suppress-common-lines + --tabsize=COLUMNS --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 '--side-by-side' ('-y') +option (*note Side by Side::). + + +File: diffutils.info-t, Node: Merge Commands, Prev: sdiff Option Summary, Up: Interactive Merging + +9.2 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' +'e1' + Edit a copy of the left version, then copy the result to the + output. + +'er' +'e2' + Edit a copy of the right version, then copy the result to the + output. + +'l' +'1' + Copy the left version to the output. + +'q' + Quit. + +'r' +'2' + 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: diffutils.info-t, Node: Merging with patch, Next: Making Patches, Prev: Interactive Merging, Up: Top + +10 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: diffutils.info-t, Node: patch Input, Next: Revision Control, Up: Merging with patch + +10.1 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: diffutils.info-t, Node: Revision Control, Next: Imperfect, Prev: patch Input, Up: Merging with patch + +10.2 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 '--get=NUM' ('-g NUM') option 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: diffutils.info-t, Node: Imperfect, Next: Creating and Removing, Prev: Revision Control, Up: Merging with patch + +10.3 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: diffutils.info-t, Node: Changed White Space, Next: Reversed Patches, Up: Imperfect + +10.3.1 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: diffutils.info-t, Node: Reversed Patches, Next: Inexact, Prev: Changed White Space, Up: Imperfect + +10.3.2 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 '--reverse' ('-R') 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: diffutils.info-t, Node: Inexact, Next: Dry Runs, Prev: Reversed Patches, Up: Imperfect + +10.3.3 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 '--fuzz=LINES' ('-F 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: diffutils.info-t, Node: Dry Runs, Prev: Inexact, Up: Imperfect + +10.3.4 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: diffutils.info-t, Node: Creating and Removing, Next: Patching Time Stamps, Prev: Imperfect, Up: Merging with patch + +10.4 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 '--new-file' ('-N') +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 +'--remove-empty-files' ('-E') 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: diffutils.info-t, Node: Patching Time Stamps, Next: Multiple Patches, Prev: Creating and Removing, Up: Merging with patch + +10.5 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 '--set-utc' ('-Z') 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 '--set-time' ('-T') 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 '--set-utc' +('-Z'). + + '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 '--force' ('-f') 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: diffutils.info-t, Node: Multiple Patches, Next: patch Directories, Prev: Patching Time Stamps, Up: Merging with patch + +10.6 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: diffutils.info-t, Node: patch Directories, Next: Backups, Prev: Multiple Patches, Up: Merging with patch + +10.7 Applying Patches in Other Directories +========================================== + +The '--directory=DIRECTORY' ('-d 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 +'--strip=NUMBER' ('-pNUMBER') 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: diffutils.info-t, Node: Backups, Next: Backup Names, Prev: patch Directories, Up: Merging with patch + +10.8 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 '--backup' ('-b') 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: diffutils.info-t, Node: Backup Names, Next: Reject Names, Prev: Backups, Up: Merging with patch + +10.9 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 +(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 '--prefix=PREFIX' ('-B PREFIX') +option makes backup files by prepending PREFIX to them. The +'--basename-prefix=PREFIX' ('-Y 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: diffutils.info-t, Node: Reject Names, Next: patch Messages, Prev: Backup Names, Up: Merging with patch + +10.10 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 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: diffutils.info-t, Node: patch Messages, Next: patch and POSIX, Prev: Reject Names, Up: Merging with patch + +10.11 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: diffutils.info-t, Node: More or Fewer Messages, Next: patch and Keyboard Input, Up: patch Messages + +10.11.1 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: diffutils.info-t, Node: patch and Keyboard Input, Next: patch Quoting Style, Prev: More or Fewer Messages, Up: patch Messages + +10.11.2 Inhibiting Keyboard Input +--------------------------------- + +There are two ways you can prevent 'patch' from asking you any +questions. The '--force' ('-f') 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 '--batch' ('-t') 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: diffutils.info-t, Node: patch Quoting Style, Prev: patch and Keyboard Input, Up: patch Messages + +10.11.3 '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: diffutils.info-t, Node: patch and POSIX, Next: patch and Tradition, Prev: patch Messages, Up: Merging with patch + +10.12 '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: diffutils.info-t, Node: patch and Tradition, Prev: patch and POSIX, Up: Merging with patch + +10.13 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 '--backup' ('-b') 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: diffutils.info-t, Node: Making Patches, Next: Invoking cmp, Prev: Merging with patch, Up: Top + +11 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: diffutils.info-t, Node: Tips for Patch Producers, Next: Tips for Patch Consumers, Up: Making Patches + +11.1 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: diffutils.info-t, Node: Tips for Patch Consumers, Next: Avoiding Common Mistakes, Prev: Tips for Patch Producers, Up: Making Patches + +11.2 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: diffutils.info-t, Node: Avoiding Common Mistakes, Next: Generating Smaller Patches, Prev: Tips for Patch Consumers, Up: Making Patches + +11.3 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: diffutils.info-t, Node: Generating Smaller Patches, Prev: Avoiding Common Mistakes, Up: Making Patches + +11.4 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: diffutils.info-t, Node: Invoking cmp, Next: Invoking diff, Prev: Making Patches, Up: Top + +12 Invoking 'cmp' +***************** + +The 'cmp' command compares two files, and if they differ, tells the +first byte and line number where they differ or reports that one file is +a prefix of the other. 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. + + By default, 'cmp' outputs nothing if the two files have the same +contents. If one file is a prefix of the other, 'cmp' prints to +standard error a message of the following form: + + cmp: EOF on SHORTER-FILE + + Otherwise, 'cmp' prints to standard output a message of the following +form: + + FROM-FILE TO-FILE differ: char BYTE-NUMBER, line LINE-NUMBER + + The message formats can differ outside the POSIX locale. Also, POSIX +allows the EOF message to be followed by a blank and some additional +information. + + 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: diffutils.info-t, Node: cmp Options, Up: Invoking cmp + +12.1 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' + Output the (decimal) byte numbers and (octal) values of all + differing bytes, instead of the default standard output. Each + output line contains a differing byte's number relative to the + start of the input, followed by the differing byte values. Byte + numbers start at 1. Also, output the EOF message if one file is + shorter than the other. + +'-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: diffutils.info-t, Node: Invoking diff, Next: Invoking diff3, Prev: Invoking cmp, Up: Top + +13 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 the standard input. + + 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 '--recursive' ('-r') 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: diffutils.info-t, Node: diff Options, Up: Invoking diff + +13.1 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::. + +'--color [=WHEN]' + Specify whether to use color for distinguishing different contexts, + like header, added or removed lines. WHEN may be omitted, or one + of: + * none Do not use color at all. This is the default when no + -color option is specified. + * auto Use color only if standard output is a terminal. + * always Always use color. + Specifying '--color' and no WHEN is equivalent to '--color=auto'. + +'-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. + + For compatibility 'diff' also supports an obsolete option syntax + '-LINES' that has effect when combined with '-c', '-p', or '-u'. + New scripts should use '-U LINES' ('-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 Lines::. + +'--ignore-file-name-case' + Ignore case when comparing file names. For example, recursive + comparison of 'd' to 'e' might compare the contents of 'd/Init' and + 'e/inIt'. At the top level, 'diff d inIt' might compare the + contents of 'd/Init' and 'inIt'. *Note Comparing Directories::. + +'-l' +'--paginate' + Pass the output through 'pr' to paginate it. *Note Pagination::. + +'-L LABEL' +'--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' + If one file is missing, treat it as present but empty. *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::. + +'--no-dereference' + Act on symbolic links themselves instead of what they point to. + Two symbolic links are deemed equal only when each points to + precisely the same name. + +'--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::. + +'--palette=PALETTE' + Specify what color palette to use when colored output is enabled. + It defaults to 'rs=0:hd=1:ad=32:de=31:ln=36' for red deleted lines, + green added lines, cyan line numbers, bold header. + + Supported capabilities are as follows. + + 'ad=32' + + SGR substring for added lines. The default is green + foreground. + + 'de=31' + + SGR substring for deleted lines. The default is red + foreground. + + 'hd=1' + + SGR substring for chunk header. The default is bold + foreground. + + 'ln=36' + + SGR substring for line numbers. The default is cyan + foreground. + +'-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::. + +'--tabsize=COLUMNS' + Assume that tab stops are set every COLUMNS (default 8) print + columns. *Note Tabs::. + +'--suppress-blank-empty' + Suppress any blanks before newlines when printing the + representation of an empty line, when outputting normal, context, + or unified format. *Note Trailing Blanks::. + +'--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' + If a first file is missing, treat it as present but empty. *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::. + +'-Z' +'--ignore-trailing-space' + Ignore white space at line end. *Note White Space::. + + +File: diffutils.info-t, Node: Invoking diff3, Next: Invoking patch, Prev: Invoking diff, Up: Top + +14 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: diffutils.info-t, Node: diff3 Options, Up: Invoking diff3 + +14.1 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::. + +'--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 --label X --label Y --label 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::. + +'--strip-trailing-cr' + Strip any trailing carriage return at the end of an input line. + *Note Binary::. + +'-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: diffutils.info-t, Node: Invoking patch, Next: Invoking sdiff, Prev: Invoking diff3, Up: Top + +15 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: diffutils.info-t, Node: patch Options, Up: Invoking patch + +15.1 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: diffutils.info-t, Node: Invoking sdiff, Next: Standards conformance, Prev: Invoking patch, Up: Top + +16 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 '--output' ('-o') produces a side-by-side difference. +This usage is obsolete; use the '--side-by-side' ('-y') 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: diffutils.info-t, Node: sdiff Options, Up: Invoking sdiff + +16.1 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 Lines::. + +'-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::. + +'--tabsize=COLUMNS' + Assume that tab stops are set every COLUMNS (default 8) print + columns. *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'. + +'-Z' +'--ignore-trailing-space' + Ignore white space at line end. *Note White Space::. + + +File: diffutils.info-t, Node: Standards conformance, Next: Projects, Prev: Invoking sdiff, Up: Top + +17 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: diffutils.info-t, Node: Projects, Next: Copying This Manual, Prev: Standards conformance, Up: Top + +18 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 <gvc@gnu.org> to +coordinate with other volunteers. + +* Menu: + +* Shortcomings:: Suggested projects for improvements. +* Bugs:: Reporting bugs. + + +File: diffutils.info-t, Node: Shortcomings, Next: Bugs, Up: Projects + +18.1 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: diffutils.info-t, Node: Internationalization, Next: Changing Structure, Up: Shortcomings + +18.1.1 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 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: diffutils.info-t, Node: Changing Structure, Next: Special Files, Prev: Internationalization, Up: Shortcomings + +18.1.2 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: diffutils.info-t, Node: Special Files, Next: Unusual File Names, Prev: Changing Structure, Up: Shortcomings + +18.1.3 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 as if they were the +pointed-to files, except that a recursive 'diff' reports an error if it +detects infinite loops of symbolic links (e.g., symbolic links to '..'). +'diff' 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: diffutils.info-t, Node: Unusual File Names, Next: Time Stamp Order, Prev: Special Files, Up: Shortcomings + +18.1.4 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: diffutils.info-t, Node: Time Stamp Order, Next: Ignoring Changes, Prev: Unusual File Names, Up: Shortcomings + +18.1.5 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: diffutils.info-t, Node: Ignoring Changes, Next: Speedups, Prev: Time Stamp Order, Up: Shortcomings + +18.1.6 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: diffutils.info-t, Node: Speedups, Prev: Ignoring Changes, Up: Shortcomings + +18.1.7 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: diffutils.info-t, Node: Bugs, Prev: Shortcomings, Up: Projects + +18.2 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-diffutils) +<bug-diffutils@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: diffutils.info-t, Node: Copying This Manual, Next: Translations, Prev: Projects, Up: Top + +Appendix A Copying This Manual +****************************** + + Version 1.3, 3 November 2008 + + Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. + <http://fsf.org/> + + 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 + functional and useful 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 your rights have been terminated and not + permanently reinstated, receipt of a copy of some or all of the + same material does not give you any rights to use it. + + 10. 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 + <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. If the Document specifies that a proxy can + decide which future versions of this License can be used, that + proxy's public statement of acceptance of a version permanently + authorizes you to choose that version for the Document. + + 11. RELICENSING + + "Massive Multiauthor Collaboration Site" (or "MMC Site") means any + World Wide Web server that publishes copyrightable works and also + provides prominent facilities for anybody to edit those works. A + public wiki that anybody can edit is an example of such a server. + A "Massive Multiauthor Collaboration" (or "MMC") contained in the + site means any set of copyrightable works thus published on the MMC + site. + + "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 + license published by Creative Commons Corporation, a not-for-profit + corporation with a principal place of business in San Francisco, + California, as well as future copyleft versions of that license + published by that same organization. + + "Incorporate" means to publish or republish a Document, in whole or + in part, as part of another Document. + + An MMC is "eligible for relicensing" if it is licensed under this + License, and if all works that were first published under this + License somewhere other than this MMC, and subsequently + incorporated in whole or in part into the MMC, (1) had no cover + texts or invariant sections, and (2) were thus incorporated prior + to November 1, 2008. + + The operator of an MMC Site may republish an MMC contained in the + site under CC-BY-SA on the same site at any time before August 1, + 2009, provided the MMC is eligible for relicensing. + +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 1.3 + or any later version published by the Free Software Foundation; + with no Invariant Sections, no Front-Cover Texts, and no Back-Cover + Texts. A copy of the license is included in the section entitled ``GNU + Free Documentation License''. + + If you have Invariant Sections, Front-Cover Texts and Back-Cover +Texts, replace the "with...Texts." line with this: + + with the Invariant Sections being LIST THEIR TITLES, with + the Front-Cover Texts being LIST, and with the Back-Cover Texts + being LIST. + + If you have Invariant Sections without Cover Texts, or some other +combination of the three, merge those two alternatives to suit the +situation. + + 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: diffutils.info-t, Node: Translations, Next: Index, Prev: Copying This Manual, Up: Top + +Appendix B Translations of This Manual +************************************** + +Nishio Futoshi of the GNUjdoc project has prepared a Japanese +translation of this manual. Its most recent version can be found at +<http://openlab.ring.gr.jp/gnujdoc/cvsweb/cvsweb.cgi/gnujdoc/>. + + +File: diffutils.info-t, Node: Index, Prev: Translations, Up: Top + +Appendix C Index +**************** + + +* Menu: + +* ! output format: Context. (line 6) +* +- output format: Unified Format. (line 6) +* < output format: Normal. (line 6) +* <<<<<<< for marking conflicts: Marking Conflicts. (line 6) +* _POSIX2_VERSION: Standards conformance. + (line 23) +* ad capability: diff Options. (line 179) +* aligning tab stops: Tabs. (line 6) +* alternate file names: Alternate Names. (line 6) +* always color option: diff Options. (line 43) +* auto color option: diff Options. (line 42) +* backup file names: Backup Names. (line 6) +* backup file strategy: Backups. (line 6) +* binary file diff: Binary. (line 6) +* blank and tab difference suppression: White Space. (line 6) +* blank line difference suppression: Blank Lines. (line 6) +* brief difference reports: Brief. (line 6) +* bug reports: Bugs. (line 6) +* C function headings: C Function Headings. (line 6) +* C if-then-else output format: If-then-else. (line 6) +* case difference suppression: Case Folding. (line 6) +* ClearCase: Revision Control. (line 6) +* cmp invocation: Invoking cmp. (line 6) +* cmp options: cmp Options. (line 6) +* color, distinguishing different context: diff Options. (line 37) +* columnar output: Side by Side. (line 6) +* common mistakes with patches: Avoiding Common Mistakes. + (line 6) +* comparing three files: Comparing Three Files. + (line 6) +* conflict: diff3 Merging. (line 26) +* conflict marking: Marking Conflicts. (line 6) +* context output format: Context. (line 6) +* creating files: Creating and Removing. + (line 6) +* de capability: diff Options. (line 184) +* diagnostics from patch: patch Messages. (line 6) +* diff invocation: Invoking diff. (line 6) +* diff merging: Interactive Merging. (line 6) +* diff options: diff Options. (line 6) +* diff sample input: Sample diff Input. (line 6) +* diff3 hunks: diff3 Hunks. (line 6) +* diff3 invocation: Invoking diff3. (line 6) +* diff3 options: diff3 Options. (line 6) +* diff3 sample input: Sample diff3 Input. (line 6) +* directories and patch: patch Directories. (line 6) +* directory structure changes: Changing Structure. (line 6) +* dry runs for patch: Dry Runs. (line 6) +* ed script output format: ed Scripts. (line 6) +* EDITOR: Merge Commands. (line 50) +* empty files, removing: Creating and Removing. + (line 6) +* exabyte, definition of: cmp Options. (line 99) +* exbibyte, definition of: cmp Options. (line 102) +* file name alternates: Alternate Names. (line 6) +* file names with unusual characters: Unusual File Names. (line 6) +* format of diff output: Output Formats. (line 6) +* format of diff3 output: Comparing Three Files. + (line 6) +* formats for if-then-else line groups: Line Group Formats. (line 6) +* forward ed script output format: Forward ed. (line 6) +* full lines: Incomplete Lines. (line 6) +* function headings, C: C Function Headings. (line 6) +* fuzz factor when patching: Inexact. (line 6) +* gibibyte, definition of: cmp Options. (line 87) +* gigabyte, definition of: cmp Options. (line 84) +* hd capability: diff Options. (line 189) +* headings: Sections. (line 6) +* hunks: Hunks. (line 6) +* hunks for diff3: diff3 Hunks. (line 6) +* if-then-else output format: If-then-else. (line 6) +* ifdef output format: If-then-else. (line 6) +* imperfect patch application: Imperfect. (line 6) +* incomplete line merging: Merging Incomplete Lines. + (line 6) +* incomplete lines: Incomplete Lines. (line 6) +* inexact patches: Inexact. (line 6) +* inhibit messages from patch: More or Fewer Messages. + (line 6) +* interactive merging: Interactive Merging. (line 6) +* introduction: Comparison. (line 6) +* intuiting file names from patches: Multiple Patches. (line 6) +* invoking cmp: Invoking cmp. (line 6) +* invoking diff: Invoking diff. (line 6) +* invoking diff3: Invoking diff3. (line 6) +* invoking patch: Invoking patch. (line 6) +* invoking sdiff: Invoking sdiff. (line 6) +* keyboard input to patch: patch and Keyboard Input. + (line 6) +* kibibyte, definition of: cmp Options. (line 75) +* kilobyte, definition of: cmp Options. (line 71) +* LC_COLLATE: Comparing Directories. + (line 6) +* LC_NUMERIC: Line Group Formats. (line 143) +* LC_TIME: Detailed Context. (line 12) +* line formats: Line Formats. (line 6) +* line group formats: Line Group Formats. (line 6) +* ln capability: diff Options. (line 194) +* mebibyte, definition of: cmp Options. (line 82) +* megabyte, definition of: cmp Options. (line 79) +* merge commands: Merge Commands. (line 6) +* merged diff3 format: Bypassing ed. (line 6) +* merged output format: If-then-else. (line 6) +* merging from a common ancestor: diff3 Merging. (line 6) +* merging interactively: Merge Commands. (line 6) +* messages from patch: patch Messages. (line 6) +* multibyte characters: Internationalization. + (line 6) +* multiple patches: Multiple Patches. (line 6) +* newline treatment by diff: Incomplete Lines. (line 6) +* none color option: diff Options. (line 40) +* normal output format: Normal. (line 6) +* options for cmp: cmp Options. (line 6) +* options for diff: diff Options. (line 6) +* options for diff3: diff3 Options. (line 6) +* options for patch: patch Options. (line 6) +* options for sdiff: sdiff Options. (line 6) +* output formats: Output Formats. (line 6) +* overlap: diff3 Merging. (line 26) +* overlapping change, selection of: Which Changes. (line 6) +* overview of diff and patch: Overview. (line 6) +* paginating diff output: Pagination. (line 6) +* patch consumer tips: Tips for Patch Consumers. + (line 6) +* patch input format: patch Input. (line 6) +* patch invocation: Invoking patch. (line 6) +* patch messages and questions: patch Messages. (line 6) +* patch options: patch Options. (line 6) +* patch producer tips: Tips for Patch Producers. + (line 6) +* patch, common mistakes: Avoiding Common Mistakes. + (line 6) +* patches, shrinking: Generating Smaller Patches. + (line 6) +* patching directories: patch Directories. (line 6) +* PATCH_GET: Revision Control. (line 13) +* PATCH_VERSION_CONTROL: Backup Names. (line 21) +* pebibyte, definition of: cmp Options. (line 97) +* performance of diff: diff Performance. (line 6) +* petabyte, definition of: cmp Options. (line 94) +* POSIX: patch and POSIX. (line 6) +* POSIX <1>: Standards conformance. + (line 6) +* POSIXLY_CORRECT: patch and POSIX. (line 6) +* POSIXLY_CORRECT <1>: Standards conformance. + (line 6) +* projects for directories: Shortcomings. (line 6) +* quoting style: patch Quoting Style. (line 6) +* QUOTING_STYLE: patch Quoting Style. (line 26) +* RCS: Revision Control. (line 6) +* RCS script output format: RCS. (line 6) +* regular expression matching headings: Specified Headings. (line 6) +* regular expression suppression: Specified Lines. (line 6) +* reject file names: Reject Names. (line 6) +* removing empty files: Creating and Removing. + (line 6) +* reporting bugs: Bugs. (line 6) +* reversed patches: Reversed Patches. (line 6) +* revision control: Revision Control. (line 6) +* sample input for diff: Sample diff Input. (line 6) +* sample input for diff3: Sample diff3 Input. (line 6) +* SCCS: Revision Control. (line 6) +* script output formats: Scripts. (line 6) +* sdiff invocation: Invoking sdiff. (line 6) +* sdiff options: sdiff Options. (line 6) +* sdiff output format: sdiff Option Summary. + (line 6) +* section headings: Sections. (line 6) +* side by side: Side by Side. (line 6) +* side by side format: Side by Side Format. (line 6) +* SIMPLE_BACKUP_SUFFIX: Backup Names. (line 12) +* special files: Special Files. (line 6) +* specified headings: Specified Headings. (line 6) +* summarizing which files differ: Brief. (line 6) +* System V diff3 compatibility: Saving the Changed File. + (line 6) +* tab and blank difference suppression: White Space. (line 6) +* tab stop alignment: Tabs. (line 6) +* tebibyte, definition of: cmp Options. (line 92) +* terabyte, definition of: cmp Options. (line 89) +* terminal, using color iff: diff Options. (line 42) +* testing patch: Dry Runs. (line 6) +* text versus binary diff: Binary. (line 6) +* time stamp format, context diffs: Detailed Context. (line 12) +* time stamp format, unified diffs: Detailed Unified. (line 12) +* time stamps on patched files: Patching Time Stamps. + (line 6) +* traditional patch: patch and Tradition. (line 6) +* trailing blanks: Trailing Blanks. (line 6) +* two-column output: Side by Side. (line 6) +* unified output format: Unified Format. (line 6) +* unmerged change: Which Changes. (line 6) +* varying-width characters: Internationalization. + (line 6) +* verbose messages from patch: More or Fewer Messages. + (line 6) +* version control: Revision Control. (line 6) +* VERSION_CONTROL: Revision Control. (line 22) +* VERSION_CONTROL <1>: Backup Names. (line 21) +* white space in patches: Changed White Space. (line 6) +* yottabyte, definition of: cmp Options. (line 110) +* zettabyte, definition of: cmp Options. (line 104) + + + +Tag Table: +Node: Top1432 +Node: Overview3646 +Node: Comparison7200 +Node: Hunks10144 +Node: White Space11587 +Node: Blank Lines13428 +Node: Specified Lines14419 +Node: Case Folding15547 +Node: Brief15966 +Node: Binary17291 +Node: Output Formats21090 +Node: Sample diff Input21817 +Node: Context23318 +Node: Context Format24897 +Node: Example Context25691 +Node: Less Context27201 +Node: Detailed Context28393 +Node: Unified Format30593 +Node: Example Unified31392 +Node: Detailed Unified32432 +Node: Sections34076 +Node: Specified Headings34837 +Node: C Function Headings36388 +Node: Alternate Names37236 +Node: Side by Side38151 +Node: Side by Side Format40303 +Node: Example Side by Side41207 +Node: Normal42549 +Node: Example Normal43552 +Node: Detailed Normal44291 +Node: Scripts46032 +Node: ed Scripts46439 +Node: Example ed47647 +Node: Detailed ed48099 +Node: Forward ed49860 +Node: RCS50638 +Node: If-then-else51856 +Node: Line Group Formats53536 +Node: Line Formats59419 +Node: Example If-then-else62690 +Node: Detailed If-then-else63771 +Node: Incomplete Lines65658 +Node: Comparing Directories67296 +Node: Adjusting Output71590 +Node: Tabs72099 +Node: Trailing Blanks73715 +Node: Pagination74942 +Node: diff Performance75412 +Node: Comparing Three Files78503 +Node: Sample diff3 Input79383 +Node: Example diff3 Normal80333 +Node: Detailed diff3 Normal81399 +Node: diff3 Hunks83189 +Node: diff3 Merging84457 +Node: Which Changes86704 +Node: Marking Conflicts88106 +Node: Bypassing ed90563 +Node: Merging Incomplete Lines91908 +Node: Saving the Changed File92636 +Node: Interactive Merging93254 +Node: sdiff Option Summary93965 +Node: Merge Commands95170 +Node: Merging with patch96461 +Node: patch Input98832 +Node: Revision Control99516 +Node: Imperfect100689 +Node: Changed White Space101840 +Node: Reversed Patches102639 +Node: Inexact104105 +Node: Dry Runs107663 +Node: Creating and Removing108529 +Node: Patching Time Stamps109581 +Node: Multiple Patches111782 +Node: patch Directories114446 +Node: Backups116072 +Node: Backup Names117139 +Ref: Backup Names-Footnote-1120096 +Node: Reject Names120223 +Node: patch Messages120814 +Node: More or Fewer Messages121876 +Node: patch and Keyboard Input122509 +Node: patch Quoting Style123540 +Node: patch and POSIX124688 +Node: patch and Tradition125529 +Node: Making Patches128953 +Node: Tips for Patch Producers129781 +Node: Tips for Patch Consumers131039 +Node: Avoiding Common Mistakes131678 +Node: Generating Smaller Patches134205 +Node: Invoking cmp135967 +Node: cmp Options137391 +Node: Invoking diff141037 +Node: diff Options142658 +Node: Invoking diff3152509 +Node: diff3 Options153149 +Node: Invoking patch156184 +Node: patch Options157394 +Node: Invoking sdiff162623 +Node: sdiff Options163767 +Node: Standards conformance166741 +Node: Projects168489 +Node: Shortcomings169203 +Node: Internationalization170307 +Node: Changing Structure171475 +Node: Special Files172581 +Node: Unusual File Names173694 +Node: Time Stamp Order174335 +Node: Ignoring Changes174980 +Node: Speedups175752 +Node: Bugs176218 +Node: Copying This Manual177073 +Node: Translations202194 +Node: Index202568 + +End Tag Table |