1 .\" $OpenBSD: patch.1,v 1.22 2008/06/06 20:44:00 jmc Exp $
2 .\" $DragonFly: src/usr.bin/patch/patch.1,v 1.10 2008/08/18 19:15:55 joerg Exp $
3 .\" $NetBSD: patch.1,v 1.19 2015/08/02 12:19:12 wiz Exp $
4 .\" Copyright 1986, Larry Wall
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29 .Nd apply a diff file to an original
33 .Op Fl B Ar backup-prefix
39 .Op Fl p Ar strip-count
41 .Op Fl V Cm t | nil | never | none
43 .Op Fl z Ar backup-ext
45 .Op Ar origfile Op Ar patchfile
47 .Pf \*(Lt Ar patchfile
50 will take a patch file containing any of the four forms of difference
51 listing produced by the
53 program and apply those differences to an original file,
54 producing a patched version.
57 is omitted, or is a hyphen, the patch will be read from the standard input.
60 will attempt to determine the type of the diff listing, unless over-ruled by a
67 Context diffs (old-style, new-style, and unified) and
68 normal diffs are applied directly by the
70 program itself, whereas ed diffs are simply fed to the
76 contains more than one patch,
78 will try to apply each of them as if they came from separate patch files.
79 This means, among other things, that it is assumed that the name of the file
80 to patch must be determined for each diff listing, and that the garbage before
81 each diff listing will be examined for interesting things such as file names
82 and revision level (see the section on
83 .Sx Filename Determination
86 The options are as follows:
88 .It Fl B Ar backup-prefix , Fl Fl prefix Ar backup-prefix
89 Causes the next argument to be interpreted as a prefix to the backup file
91 If this argument is specified, any argument to
94 .It Fl b , Fl Fl backup
95 Save a backup copy of the file before it is modified.
96 By default the original file is saved with a backup extension of
98 unless the file already has a numbered backup, in which case a numbered
100 This is equivalent to specifying
101 .Qo Fl V Cm existing Qc .
102 This option is currently the default, unless
105 .It Fl C , Fl Fl check
106 Checks that the patch would apply cleanly, but does not modify anything.
107 .It Fl c , Fl Fl context
110 to interpret the patch file as a context diff.
111 .It Fl D Ar symbol , Fl Fl ifdef Ar symbol
116 construct to mark changes.
117 The argument following will be used as the differentiating symbol.
118 Note that, unlike the C compiler, there must be a space between the
121 .It Fl d Ar directory , Fl Fl directory Ar directory
124 to interpret the next argument as a directory,
125 and change the working directory to it before doing anything else.
126 .It Fl E , Fl Fl remove-empty-files
129 to remove output files that are empty after the patches have been applied.
130 This option is useful when applying patches that create or remove files.
134 to interpret the patch file as an
137 .It Fl F Ar max-fuzz , Fl Fl fuzz Ar max-fuzz
138 Sets the maximum fuzz factor.
139 This option only applies to context diffs, and causes
141 to ignore up to that many lines in looking for places to install a hunk.
142 Note that a larger fuzz factor increases the odds of a faulty patch.
143 The default fuzz factor is 2, and it may not be set to more than
144 the number of lines of context in the context diff, ordinarily 3.
145 .It Fl f , Fl Fl force
148 to assume that the user knows exactly what he or she is doing, and to not
150 It assumes the following:
151 skip patches for which a file to patch can't be found;
152 patch files even though they have the wrong version for the
155 and assume that patches are not reversed even if they look like they are.
156 This option does not suppress commentary; use
159 .It Fl i Ar patchfile , Fl Fl input Ar patchfile
160 Causes the next argument to be interpreted as the input file name
162 This option may be specified multiple times.
163 .It Fl l , Fl Fl ignore-whitespace
164 Causes the pattern matching to be done loosely, in case the tabs and
165 spaces have been munged in your input file.
166 Any sequence of whitespace in the pattern line will match any sequence
168 Normal characters must still match exactly.
169 Each line of the context must still match a line in the input file.
170 .It Fl N , Fl Fl forward
173 to ignore patches that it thinks are reversed or already applied.
176 .It Fl n , Fl Fl normal
179 to interpret the patch file as a normal diff.
180 .It Fl o Ar out-file , Fl Fl output Ar out-file
181 Causes the next argument to be interpreted as the output file name.
182 .It Fl p Ar strip-count , Fl Fl strip Ar strip-count
183 Sets the pathname strip count,
184 which controls how pathnames found in the patch file are treated,
185 in case you keep your files in a different directory than the person who sent
187 The strip count specifies how many slashes are to be stripped from
188 the front of the pathname.
189 (Any intervening directory names also go away.)
190 For example, supposing the file name in the patch file was
191 .Pa /u/howard/src/blurfl/blurfl.c :
195 gives the entire pathname unmodified.
200 .D1 Pa u/howard/src/blurfl/blurfl.c
202 without the leading slash.
207 .D1 Pa blurfl/blurfl.c
211 at all just gives you
213 unless all of the directories in the leading path
214 .Pq Pa u/howard/src/blurfl
215 exist and that path is relative,
216 in which case you get the entire pathname unmodified.
217 Whatever you end up with is looked for either in the current directory,
218 or the directory specified by the
221 .It Fl R , Fl Fl reverse
224 that this patch was created with the old and new files swapped.
225 (Yes, I'm afraid that does happen occasionally, human nature being what it
228 will attempt to swap each hunk around before applying it.
229 Rejects will come out in the swapped format.
232 option will not work with ed diff scripts because there is too little
233 information to reconstruct the reverse operation.
235 If the first hunk of a patch fails,
237 will reverse the hunk to see if it can be applied that way.
238 If it can, you will be asked if you want to have the
241 If it can't, the patch will continue to be applied normally.
242 (Note: this method cannot detect a reversed patch if it is a normal diff
243 and if the first command is an append (i.e., it should have been a delete)
244 since appends always succeed, due to the fact that a null context will match
246 Luckily, most patches add or change lines rather than delete them, so most
247 reversed normal diffs will begin with a delete, which will fail, triggering
249 .It Fl r Ar rej-name , Fl Fl reject-file Ar rej-name
250 Causes the next argument to be interpreted as the reject file name.
251 .It Fl s , Fl Fl quiet , Fl Fl silent
254 do its work silently, unless an error occurs.
255 .It Fl t , Fl Fl batch
258 in that it suppresses questions, but makes some different assumptions:
259 skip patches for which a file to patch can't be found (the same as
261 skip patches for which the file has the wrong version for the
264 and assume that patches are reversed if they look like they are.
265 .It Fl u , Fl Fl unified
268 to interpret the patch file as a unified context diff (a unidiff).
269 .It Fl V Cm t | nil | never | none , Fl Fl version-control Cm t | nil | never | none
270 Causes the next argument to be interpreted as a method for creating
272 The type of backups made can also be given in the
273 .Ev PATCH_VERSION_CONTROL
276 environment variables, which are overridden by this option.
279 option overrides this option, causing the prefix to always be used for
280 making backup file names.
282 .Ev PATCH_VERSION_CONTROL
285 environment variables and the argument to the
287 option are like the GNU Emacs
289 variable; they also recognize synonyms that are more descriptive.
290 The valid values are (unique abbreviations are accepted):
291 .Bl -tag -width Ds -offset indent
293 Always make numbered backups.
294 .It Cm nil , existing
295 Make numbered backups of files that already have them,
296 simple backups of the others.
297 .It Cm never , simple
298 Always make simple backups.
300 .It Fl v , Fl Fl version
303 to print out its revision header and patch level.
304 .It Fl x Ar number , Fl Fl debug Ar number
305 Sets internal debugging flags, and is of interest only to
308 .It Fl z Ar backup-ext , Fl Fl suffix Ar backup-ext
309 Causes the next argument to be interpreted as the backup extension, to be
315 conformance, specifically:
318 Backup files are not created unless the
322 If unspecified, the file name used is the first of the old, new and
323 index files that exists.
326 .Ss Patch Application
328 will try to skip any leading garbage, apply the diff,
329 and then skip any trailing garbage.
330 Thus you could feed an article or message containing a
334 If the entire diff is indented by a consistent amount,
335 this will be taken into account.
337 With context diffs, and to a lesser extent with normal diffs,
339 can detect when the line numbers mentioned in the patch are incorrect,
340 and will attempt to find the correct place to apply each hunk of the patch.
341 As a first guess, it takes the line number mentioned for the hunk, plus or
342 minus any offset used in applying the previous hunk.
343 If that is not the correct place,
345 will scan both forwards and backwards for a set of lines matching the context
349 looks for a place where all lines of the context match.
350 If no such place is found, and it's a context diff, and the maximum fuzz factor
351 is set to 1 or more, then another scan takes place ignoring the first and last
353 If that fails, and the maximum fuzz factor is set to 2 or more,
354 the first two and last two lines of context are ignored,
355 and another scan is made.
356 .Pq The default maximum fuzz factor is 2.
360 cannot find a place to install that hunk of the patch, it will put the hunk
361 out to a reject file, which normally is the name of the output file plus
363 (Note that the rejected hunk will come out in context diff form whether the
364 input patch was a context diff or a normal diff.
365 If the input was a normal diff, many of the contexts will simply be null.)
366 The line numbers on the hunks in the reject file may be different than
367 in the patch file: they reflect the approximate location patch thinks the
368 failed hunks belong in the new file rather than the old one.
370 As each hunk is completed, you will be told whether the hunk succeeded or
371 failed, and which line (in the new file)
373 thought the hunk should go on.
374 If this is different from the line number specified in the diff,
375 you will be told the offset.
376 A single large offset MAY be an indication that a hunk was installed in the
378 You will also be told if a fuzz factor was used to make the match, in which
379 case you should also be slightly suspicious.
380 .Ss Filename Determination
381 If no original file is specified on the command line,
383 will try to figure out from the leading garbage what the name of the file
385 When checking a prospective file name, pathname components are stripped
388 option and the file's existence and writability are checked relative
389 to the current working directory (or the directory specified by the
393 If the diff is a context or unified diff,
395 is able to determine the old and new file names from the diff header.
396 For context diffs, the
398 file is specified in the line beginning with
402 file is specified in the line beginning with
404 For a unified diff, the
406 file is specified in the line beginning with
410 file is specified in the line beginning with
414 line in the leading garbage (regardless of the diff type),
416 will use the file name from that line as the
421 will choose the file name by performing the following steps, with the first
427 is operating in strict
429 mode, the first of the
434 file names that exist is used.
437 will examine either the
441 file names or, for a non-context diff, the
443 file name, and choose the file name with the fewest path components,
444 the shortest basename, and the shortest total file name length (in that order).
448 checks for the existence of the files in an RCS directory using the criteria
452 will attempt to get or check out the file.
454 If no suitable file was found to patch, the patch file is a context or
455 unified diff, and the old file was zero length, the new file name is
458 If the file name still cannot be determined,
460 will prompt the user for the file name to use.
463 Additionally, if the leading garbage contains a
467 will take the first word from the prerequisites line (normally a version
468 number) and check the input file to see if that word can be found.
471 will ask for confirmation before proceeding.
473 The upshot of all this is that you should be able to say, while in a news
474 interface, the following:
476 .Dl | patch -d /usr/src/local/blurfl
478 and patch a file in the blurfl directory directly from the article containing
481 By default, the patched version is put in place of the original, with
482 the original file backed up to the same name with the extension
484 or as specified by the
490 The extension used for making backup files may also be specified in the
491 .Ev SIMPLE_BACKUP_SUFFIX
492 environment variable, which is overridden by the options above.
494 If the backup file is a symbolic or hard link to the original file,
496 creates a new backup file name by changing the first lowercase letter
497 in the last component of the file's name into uppercase.
498 If there are no more lowercase letters in the name,
499 it removes the first character from the name.
500 It repeats this process until it comes up with a
501 backup file that does not already exist or is not linked to the original file.
503 You may also specify where you want the output to go with the
505 option; if that file already exists, it is backed up first.
506 .Ss Notes For Patch Senders
507 There are several things you should bear in mind if you are going to
508 be sending out patches:
510 First, you can save people a lot of grief by keeping a
512 file which is patched to increment the patch level as the first diff in the
513 patch file you send out.
516 line in with the patch, it won't let them apply
517 patches out of order without some warning.
519 Second, make sure you've specified the file names right, either in a
520 context diff header, or with an
523 If you are patching something in a subdirectory, be sure to tell the patch
528 Third, you can create a file by sending out a diff that compares a
529 null file to the file you want to create.
530 This will only work if the file you want to create doesn't exist already in
531 the target directory.
533 Fourth, take care not to send out reversed patches, since it makes people wonder
534 whether they already applied the patch.
536 Fifth, while you may be able to get away with putting 582 diff listings into
537 one file, it is probably wiser to group related patches into separate files in
538 case something goes haywire.
540 .Bl -tag -width "PATCH_VERSION_CONTROL" -compact
541 .It Ev POSIXLY_CORRECT
546 option has been specified.
547 .It Ev SIMPLE_BACKUP_SUFFIX
548 Extension to use for backup file names instead of
551 Directory to put temporary files in; default is
553 .It Ev PATCH_VERSION_CONTROL
554 Selects when numbered backup files are made.
555 .It Ev VERSION_CONTROL
557 .Ev PATCH_VERSION_CONTROL .
560 .Bl -tag -width "$TMPDIR/patch*" -compact
561 .It Pa $TMPDIR/patch*
565 used to read input when
570 Too many to list here, but generally indicative that
572 couldn't parse your patch file.
576 indicates that there is unprocessed text in the patch file and that
578 is attempting to intuit whether there is a patch in that text and, if so,
579 what kind of patch it is.
583 utility exits with one of the following values:
585 .Bl -tag -width Ds -compact -offset indent
587 Successful completion.
589 One or more lines were written to a reject file.
594 When applying a set of patches in a loop it behooves you to check this
595 exit status so you don't apply a later patch to a partially patched file.
601 utility is compliant with the
604 (except as detailed above for the
607 though the presence of
615 are extensions to that specification.
618 with many other contributors.
621 cannot tell if the line numbers are off in an ed script, and can only detect
622 bad line numbers in a normal diff when it finds a
627 A context diff using fuzz factor 3 may have the same problem.
628 Until a suitable interactive interface is added, you should probably do
629 a context diff in these cases to see if the changes made sense.
630 Of course, compiling without errors is a pretty good indication that the patch
631 worked, but not always.
634 usually produces the correct results, even when it has to do a lot of
636 However, the results are guaranteed to be correct only when the patch is
637 applied to exactly the same version of the file that the patch was
640 Could be smarter about partial matches, excessively deviant offsets and
641 swapped code, but that would take an extra pass.
645 will fail if you try to check several patches in succession that build on
649 code would have to be restructured to keep temporary files around so that it
650 can handle this situation.
652 If code has been duplicated (for instance with #ifdef OLDCODE ... #else ...
655 is incapable of patching both versions, and, if it works at all, will likely
656 patch the wrong one, and tell you that it succeeded to boot.
658 If you apply a patch you've already applied,
660 will think it is a reversed patch, and offer to un-apply the patch.
661 This could be construed as a feature.