1 .\" $OpenBSD: patch.1,v 1.22 2008/06/06 20:44:00 jmc Exp $
2 .\" Copyright 1986, Larry Wall
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27 .Nd apply a diff file to an original
32 .Op Fl B Ar backup-prefix
38 .Op Fl p Ar strip-count
40 .Op Fl V Cm t | nil | never
42 .Op Fl z Ar backup-ext
44 .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:
89 .Fl B Ar backup-prefix ,
90 .Fl Fl prefix Ar backup-prefix
92 Causes the next argument to be interpreted as a prefix to the backup file
94 If this argument is specified, any argument to
97 .It Fl b , Fl Fl backup
98 Save a backup copy of the file before it is modified.
99 By default the original file is saved with a backup extension of
101 unless the file already has a numbered backup, in which case a numbered
103 This is equivalent to specifying
104 .Qo Fl V Cm existing Qc .
105 This option is currently the default, unless
108 .It Fl C , Fl Fl check
109 Checks that the patch would apply cleanly, but does not modify anything.
110 .It Fl c , Fl Fl context
113 to interpret the patch file as a context diff.
116 .Fl Fl ifdef Ar symbol
122 construct to mark changes.
123 The argument following will be used as the differentiating symbol.
124 Note that, unlike the C compiler, there must be a space between the
129 .Fl Fl directory Ar directory
133 to interpret the next argument as a directory,
134 and change the working directory to it before doing anything else.
135 .It Fl E , Fl Fl remove-empty-files
138 to remove output files that are empty after the patches have been applied.
139 This option is useful when applying patches that create or remove files.
143 to interpret the patch file as an
148 .Fl Fl fuzz Ar max-fuzz
150 Sets the maximum fuzz factor.
151 This option only applies to context diffs, and causes
153 to ignore up to that many lines in looking for places to install a hunk.
154 Note that a larger fuzz factor increases the odds of a faulty patch.
155 The default fuzz factor is 2, and it may not be set to more than
156 the number of lines of context in the context diff, ordinarily 3.
157 .It Fl f , Fl Fl force
160 to assume that the user knows exactly what he or she is doing, and to not
162 It assumes the following:
163 skip patches for which a file to patch can't be found;
164 patch files even though they have the wrong version for the
167 and assume that patches are not reversed even if they look like they are.
168 This option does not suppress commentary; use
173 .Fl Fl input Ar patchfile
175 Causes the next argument to be interpreted as the input file name
177 This option may be specified multiple times.
178 .It Fl l , Fl Fl ignore-whitespace
179 Causes the pattern matching to be done loosely, in case the tabs and
180 spaces have been munged in your input file.
181 Any sequence of whitespace in the pattern line will match any sequence
183 Normal characters must still match exactly.
184 Each line of the context must still match a line in the input file.
185 .It Fl N , Fl Fl forward
188 to ignore patches that it thinks are reversed or already applied.
191 .It Fl n , Fl Fl normal
194 to interpret the patch file as a normal diff.
197 .Fl Fl output Ar out-file
199 Causes the next argument to be interpreted as the output file name.
201 .Fl p Ar strip-count ,
202 .Fl Fl strip Ar strip-count
204 Sets the pathname strip count,
205 which controls how pathnames found in the patch file are treated,
206 in case you keep your files in a different directory than the person who sent
208 The strip count specifies how many slashes are to be stripped from
209 the front of the pathname.
210 (Any intervening directory names also go away.)
211 For example, supposing the file name in the patch file was
212 .Pa /u/howard/src/blurfl/blurfl.c :
216 gives the entire pathname unmodified.
221 .D1 Pa u/howard/src/blurfl/blurfl.c
223 without the leading slash.
228 .D1 Pa blurfl/blurfl.c
232 at all just gives you
234 unless all of the directories in the leading path
235 .Pq Pa u/howard/src/blurfl
236 exist and that path is relative,
237 in which case you get the entire pathname unmodified.
238 Whatever you end up with is looked for either in the current directory,
239 or the directory specified by the
242 .It Fl R , Fl Fl reverse
245 that this patch was created with the old and new files swapped.
246 (Yes, I'm afraid that does happen occasionally, human nature being what it
249 will attempt to swap each hunk around before applying it.
250 Rejects will come out in the swapped format.
253 option will not work with ed diff scripts because there is too little
254 information to reconstruct the reverse operation.
256 If the first hunk of a patch fails,
258 will reverse the hunk to see if it can be applied that way.
259 If it can, you will be asked if you want to have the
262 If it can't, the patch will continue to be applied normally.
263 (Note: this method cannot detect a reversed patch if it is a normal diff
264 and if the first command is an append (i.e. it should have been a delete)
265 since appends always succeed, due to the fact that a null context will match
267 Luckily, most patches add or change lines rather than delete them, so most
268 reversed normal diffs will begin with a delete, which will fail, triggering
272 .Fl Fl reject-file Ar rej-name
274 Causes the next argument to be interpreted as the reject file name.
276 .Fl s , Fl Fl quiet ,
281 do its work silently, unless an error occurs.
282 .It Fl t , Fl Fl batch
285 in that it suppresses questions, but makes some different assumptions:
286 skip patches for which a file to patch can't be found (the same as
288 skip patches for which the file has the wrong version for the
291 and assume that patches are reversed if they look like they are.
292 .It Fl u , Fl Fl unified
295 to interpret the patch file as a unified context diff (a unidiff).
297 .Fl V Cm t | nil | never ,
298 .Fl Fl version-control Cm t | nil | never
300 Causes the next argument to be interpreted as a method for creating
302 The type of backups made can also be given in the
303 .Ev PATCH_VERSION_CONTROL
306 environment variables, which are overridden by this option.
309 option overrides this option, causing the prefix to always be used for
310 making backup file names.
312 .Ev PATCH_VERSION_CONTROL
315 environment variables and the argument to the
317 option are like the GNU Emacs
319 variable; they also recognize synonyms that are more descriptive.
320 The valid values are (unique abbreviations are accepted):
321 .Bl -tag -width Ds -offset indent
323 Always make numbered backups.
324 .It Cm nil , existing
325 Make numbered backups of files that already have them,
326 simple backups of the others.
327 .It Cm never , simple
328 Always make simple backups.
330 .It Fl v , Fl Fl version
333 to print out its revision header and patch level.
336 .Fl Fl debug Ar number
338 Sets internal debugging flags, and is of interest only to
342 .Fl z Ar backup-ext ,
343 .Fl Fl suffix Ar backup-ext
345 Causes the next argument to be interpreted as the backup extension, to be
351 conformance, specifically:
354 Backup files are not created unless the
358 If unspecified, the file name used is the first of the old, new and
359 index files that exists.
362 .Ss Patch Application
364 will try to skip any leading garbage, apply the diff,
365 and then skip any trailing garbage.
366 Thus you could feed an article or message containing a
370 If the entire diff is indented by a consistent amount,
371 this will be taken into account.
373 With context diffs, and to a lesser extent with normal diffs,
375 can detect when the line numbers mentioned in the patch are incorrect,
376 and will attempt to find the correct place to apply each hunk of the patch.
377 As a first guess, it takes the line number mentioned for the hunk, plus or
378 minus any offset used in applying the previous hunk.
379 If that is not the correct place,
381 will scan both forwards and backwards for a set of lines matching the context
385 looks for a place where all lines of the context match.
386 If no such place is found, and it's a context diff, and the maximum fuzz factor
387 is set to 1 or more, then another scan takes place ignoring the first and last
389 If that fails, and the maximum fuzz factor is set to 2 or more,
390 the first two and last two lines of context are ignored,
391 and another scan is made.
392 .Pq The default maximum fuzz factor is 2.
396 cannot find a place to install that hunk of the patch, it will put the hunk
397 out to a reject file, which normally is the name of the output file plus
399 (Note that the rejected hunk will come out in context diff form whether the
400 input patch was a context diff or a normal diff.
401 If the input was a normal diff, many of the contexts will simply be null.)
402 The line numbers on the hunks in the reject file may be different than
403 in the patch file: they reflect the approximate location patch thinks the
404 failed hunks belong in the new file rather than the old one.
406 As each hunk is completed, you will be told whether the hunk succeeded or
407 failed, and which line (in the new file)
409 thought the hunk should go on.
410 If this is different from the line number specified in the diff,
411 you will be told the offset.
412 A single large offset MAY be an indication that a hunk was installed in the
414 You will also be told if a fuzz factor was used to make the match, in which
415 case you should also be slightly suspicious.
416 .Ss Filename Determination
417 If no original file is specified on the command line,
419 will try to figure out from the leading garbage what the name of the file
421 When checking a prospective file name, pathname components are stripped
424 option and the file's existence and writability are checked relative
425 to the current working directory (or the directory specified by the
429 If the diff is a context or unified diff,
431 is able to determine the old and new file names from the diff header.
432 For context diffs, the
434 file is specified in the line beginning with
438 file is specified in the line beginning with
440 For a unified diff, the
442 file is specified in the line beginning with
446 file is specified in the line beginning with
450 line in the leading garbage (regardless of the diff type),
452 will use the file name from that line as the
457 will choose the file name by performing the following steps, with the first
463 is operating in strict
465 mode, the first of the
470 file names that exist is used.
473 will examine either the
477 file names or, for a non-context diff, the
479 file name, and choose the file name with the fewest path components,
480 the shortest basename, and the shortest total file name length (in that order).
484 checks for the existence of the files in an SCCS or RCS directory
485 (using the appropriate prefix or suffix) using the criteria specified
489 will attempt to get or check out the file.
491 If no suitable file was found to patch, the patch file is a context or
492 unified diff, and the old file was zero length, the new file name is
495 If the file name still cannot be determined,
497 will prompt the user for the file name to use.
500 Additionally, if the leading garbage contains a
504 will take the first word from the prerequisites line (normally a version
505 number) and check the input file to see if that word can be found.
508 will ask for confirmation before proceeding.
510 The upshot of all this is that you should be able to say, while in a news
511 interface, the following:
513 .Dl | patch -d /usr/src/local/blurfl
515 and patch a file in the blurfl directory directly from the article containing
518 By default, the patched version is put in place of the original, with
519 the original file backed up to the same name with the extension
521 or as specified by the
527 The extension used for making backup files may also be specified in the
528 .Ev SIMPLE_BACKUP_SUFFIX
529 environment variable, which is overridden by the options above.
531 If the backup file is a symbolic or hard link to the original file,
533 creates a new backup file name by changing the first lowercase letter
534 in the last component of the file's name into uppercase.
535 If there are no more lowercase letters in the name,
536 it removes the first character from the name.
537 It repeats this process until it comes up with a
538 backup file that does not already exist or is not linked to the original file.
540 You may also specify where you want the output to go with the
542 option; if that file already exists, it is backed up first.
543 .Ss Notes For Patch Senders
544 There are several things you should bear in mind if you are going to
545 be sending out patches:
547 First, you can save people a lot of grief by keeping a
549 file which is patched to increment the patch level as the first diff in the
550 patch file you send out.
553 line in with the patch, it won't let them apply
554 patches out of order without some warning.
556 Second, make sure you've specified the file names right, either in a
557 context diff header, or with an
560 If you are patching something in a subdirectory, be sure to tell the patch
565 Third, you can create a file by sending out a diff that compares a
566 null file to the file you want to create.
567 This will only work if the file you want to create doesn't exist already in
568 the target directory.
570 Fourth, take care not to send out reversed patches, since it makes people wonder
571 whether they already applied the patch.
573 Fifth, while you may be able to get away with putting 582 diff listings into
574 one file, it is probably wiser to group related patches into separate files in
575 case something goes haywire.
577 .Bl -tag -width "PATCH_VERSION_CONTROL" -compact
578 .It Ev POSIXLY_CORRECT
583 option has been specified.
584 .It Ev SIMPLE_BACKUP_SUFFIX
585 Extension to use for backup file names instead of
588 Directory to put temporary files in; default is
590 .It Ev PATCH_VERSION_CONTROL
591 Selects when numbered backup files are made.
592 .It Ev VERSION_CONTROL
594 .Ev PATCH_VERSION_CONTROL .
597 .Bl -tag -width "$TMPDIR/patch*" -compact
598 .It Pa $TMPDIR/patch*
602 used to read input when
609 utility exits with one of the following values:
611 .Bl -tag -width Ds -compact -offset indent
613 Successful completion.
615 One or more lines were written to a reject file.
620 When applying a set of patches in a loop it behooves you to check this
621 exit status so you don't apply a later patch to a partially patched file.
623 Too many to list here, but generally indicative that
625 couldn't parse your patch file.
629 indicates that there is unprocessed text in the patch file and that
631 is attempting to intuit whether there is a patch in that text and, if so,
632 what kind of patch it is.
638 utility is compliant with the
641 (except as detailed above for the
644 though the presence of
652 are extensions to that specification.
655 with many other contributors.
658 cannot tell if the line numbers are off in an ed script, and can only detect
659 bad line numbers in a normal diff when it finds a
664 A context diff using fuzz factor 3 may have the same problem.
665 Until a suitable interactive interface is added, you should probably do
666 a context diff in these cases to see if the changes made sense.
667 Of course, compiling without errors is a pretty good indication that the patch
668 worked, but not always.
671 usually produces the correct results, even when it has to do a lot of
673 However, the results are guaranteed to be correct only when the patch is
674 applied to exactly the same version of the file that the patch was
677 Could be smarter about partial matches, excessively deviant offsets and
678 swapped code, but that would take an extra pass.
682 will fail if you try to check several patches in succession that build on
686 code would have to be restructured to keep temporary files around so that it
687 can handle this situation.
689 If code has been duplicated (for instance with #ifdef OLDCODE ... #else ...
692 is incapable of patching both versions, and, if it works at all, will likely
693 patch the wrong one, and tell you that it succeeded to boot.
695 If you apply a patch you've already applied,
697 will think it is a reversed patch, and offer to un-apply the patch.
698 This could be construed as a feature.
projects / dragonfly.git / blob