PATCH(1) General Commands Manual PATCH(1)
patch - apply a diff file to an original
patch [options] [originalfile [patchfile]]
but usually just
patch -pnum <patchfile
patch takes a patch file patchfile containing a difference listing
produced by the diff program and applies those differences to one or more
original files, producing patched versions. Normally the patched
versions are put in place of the originals. Backups can be made; see the
-b or --backup option. The names of the files to be patched are usually
taken from the patch file, but if there's just one file to be patched it
can specified on the command line as originalfile.
Upon startup, patch attempts to determine the type of the diff listing,
unless overruled by a -c (--context), -e (--ed), -n (--normal), or -u
(--unified) option. Context diffs (old-style, new-style, and unified)
and normal diffs are applied by the patch program itself, while ed diffs
are simply fed to the ed(1) editor via a pipe.
patch tries to skip any leading garbage, apply the diff, and then skip
any trailing garbage. Thus you could feed an article or message
containing a diff listing to patch, and it should work. If the entire
diff is indented by a consistent amount, or if a context diff contains
lines ending in CRLF or is encapsulated one or more times by prepending
"- " to lines starting with "-" as specified by Internet RFC 934, this is
taken into account. After removing indenting or encapsulation, lines
beginning with # are ignored, as they are considered to be comments.
With context diffs, and to a lesser extent with normal diffs, patch can
detect when the line numbers mentioned in the patch are incorrect, and
attempts to find the correct place to apply each hunk of the patch. As a
first guess, it takes the line number mentioned for the hunk, plus or
minus any offset used in applying the previous hunk. If that is not the
correct place, patch scans both forwards and backwards 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 no such place is found, and
it's a context diff, and the maximum fuzz factor is set to 1 or more,
then another scan takes place ignoring the first and last line of
context. If that fails, and the maximum fuzz factor is set to 2 or more,
the first two and last two lines of context are ignored, and another scan
is made. (The default maximum fuzz factor is 2.) If patch cannot find a
place to install that hunk of the patch, it puts the hunk out to a reject
file, which normally is the name of the output file plus a .rej suffix,
or # if .rej would generate a file name that is too long (if even
appending the single character # makes the file name too long, then #
replaces the file name's last character). (The rejected hunk comes out
in ordinary context diff form regardless of the input patch's form. If
the input was a normal diff, many of the contexts are simply null.) The
line numbers on the hunks in the reject file may be different than in the
patch file: they reflect the approximate location patch thinks the failed
hunks belong in the new file rather than the old one.
As each hunk is completed, you are told if the hunk failed, and if so
which line (in the new file) patch thought the hunk should go on. If the
hunk is installed at a different line from the line number specified in
the diff you are told the offset. A single large offset may indicate
that a hunk was installed in the wrong place. You are also told if a
fuzz factor was used to make the match, in which case you should also be
slightly suspicious. If the --verbose option is given, you are also told
about hunks that match exactly.
If no original file origfile is specified on the command line, patch
tries to figure out from the leading garbage what the name of the file to
edit is, using the following rules.
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, Perforce, and SCCS (see the
-g num or --get=num option), and no named files exist but an RCS,
ClearCase, Perforce, or SCCS master is found, patch selects the first
named file with an RCS, ClearCase, Perforce, or SCCS master.
• If no named files exist, no RCS, ClearCase, Perforce, 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.
Additionally, if the leading garbage contains a Prereq: line, patch takes
the first word from the prerequisites line (normally a version number)
and checks the original file to see if that word can be found. If not,
patch asks for confirmation before proceeding.
The upshot of all this is that you should be able to say, while in a news
interface, something like the following:
| patch -d /usr/src/local/blurfl
and patch a file in the blurfl directory directly from the article
containing the patch.
If the patch file contains more than one patch, patch tries to apply each
of them as if they came from separate patch files. This means, among
other things, that it is assumed that the name of the file to patch must
be determined for each diff listing, and that the garbage before each
diff listing contains interesting things such as file names and revision
level, as mentioned previously.
-b or --backup
Make backup files. That is, when patching a file, rename or copy the
original instead of removing it. When backing up a file that does not
exist, an empty, unreadable backup file is created as a placeholder to
represent the nonexistent file. See the -V or --version-control
option for details about how backup file names are determined.
Back up a file if the patch does not match the file exactly and if
backups are not otherwise requested. This is the default unless patch
is conforming to POSIX.
Do not back up a file if the patch does not match the file exactly and
if backups are not otherwise requested. This is the default if patch
is conforming to POSIX.
-B pref or --prefix=pref
Prefix pref to a file name when generating its simple backup file
name. For example, with -B /junk/ the simple backup file name for
src/patch/util.c is /junk/src/patch/util.c.
Read and write all files in binary mode, except for standard output
and /dev/tty. This option has no effect on POSIX-conforming systems.
On systems like DOS where this option makes a difference, the patch
should be generated by diff -a --binary.
-c or --context
Interpret the patch file as a ordinary context diff.
-d dir or --directory=dir
Change to the directory dir immediately, before doing anything else.
-D define or --ifdef=define
Use the #ifdef ... #endif construct to mark changes, with define as
the differentiating symbol.
Print the results of applying the patches without actually changing
-e or --ed
Interpret the patch file as an ed script.
-E or --remove-empty-files
Remove output files that are empty after the patches have been
applied. Normally this option is unnecessary, since patch can examine
the time stamps on the header to determine whether a file should exist
after patching. However, if the input is not a context diff or if
patch is conforming to POSIX, patch does not remove empty patched
files unless this option is given. When patch removes a file, it also
attempts to remove any empty ancestor directories.
-f or --force
Assume that the user knows exactly what he or she is doing, and do not
ask any questions. Skip patches whose headers do not say which file
is to be patched; patch files even though they have the wrong version
for the Prereq: line in the patch; and assume that patches are not
reversed even if they look like they are. This option does not
suppress commentary; use -s for that.
-F num or --fuzz=num
Set the maximum fuzz factor. This option only applies to diffs that
have context, and causes patch to ignore up to that many lines in
looking for places to install a hunk. Note that a larger fuzz factor
increases the odds of a faulty patch. The default fuzz factor is 2,
and it may not be set to more than the number of lines of context in
the context diff, ordinarily 3.
-g num or --get=num
This option controls patch's actions when a file is under RCS or SCCS
control, and does not exist or is read-only and matches the default
version, or when a file is under ClearCase or Perforce control and
does not exist. If num is positive, patch gets (or checks out) the
file from the revision control system; if zero, patch ignores RCS,
ClearCase, Perforce, and SCCS and does not get the file; and if
negative, patch asks the user whether to get the file. The default
value of this option 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.
Print a summary of options and exit.
-i patchfile or --input=patchfile
Read the patch from patchfile. If patchfile is -, read from standard
input, the default.
-l or --ignore-whitespace
Match patterns loosely, in case tabs or spaces have been munged in
your files. Any sequence of one or more blanks in the patch file
matches any sequence in the original file, and sequences of blanks at
the ends of lines are ignored. Normal characters must still match
exactly. Each line of the context must still match a line in the
-n or --normal
Interpret the patch file as a normal diff.
-N or --forward
Ignore patches that seem to be reversed or already applied. See also
-o outfile or --output=outfile
Send output to outfile instead of patching files in place. Do not use
this option if outfile is one of the files to be patched.
-pnum or --strip=num
Strip the smallest prefix containing num leading slashes from each
file name found in the patch file. A sequence of one or more adjacent
slashes is counted as a single slash. This controls how file names
found in the patch file are treated, in case you keep your files in a
different directory than the person who sent out the patch. For
example, supposing the file name in the patch file was
setting -p0 gives the entire file name unmodified, -p1 gives
without the leading slash, -p4 gives
and not specifying -p at all just gives you blurfl.c. Whatever you
end up with is looked for either in the current directory, or the
directory specified by the -d option.
Conform 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.
• Do not remove files that are empty after patching.
• Do not ask whether to get files from RCS, ClearCase, Perforce, or
• Require that all options precede the files in the command line.
• Do not backup files when there is a mismatch.
Use style word to quote output names. The word should be one of the
Output names as-is.
shell Quote names for the shell if they contain shell metacharacters
or would cause ambiguous output.
Quote names for the shell, even if they would normally not
c Quote names as for a C language string.
escape Quote as with c except omit the surrounding double-quote
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.
-r rejectfile or --reject-file=rejectfile
Put rejects into rejectfile instead of the default .rej file.
-R or --reverse
Assume that this patch was created with the old and new files swapped.
(Yes, I'm afraid that does happen occasionally, human nature being
what it is.) patch attempts to swap each hunk around before applying
it. Rejects come out in the swapped format. The -R option does not
work with ed diff scripts because there is too little information to
reconstruct the reverse operation.
If the first hunk of a patch fails, patch reverses the hunk to see if
it can be applied that way. If it can, you are asked if you want to
have the -R option set. If it can't, the patch continues to be
applied normally. (Note: this method cannot detect a reversed patch
if it is a normal diff and if the first command is an append (i.e. it
should have been a delete) since appends always succeed, due to the
fact that a null context matches anywhere. Luckily, most patches add
or change lines rather than delete them, so most reversed normal diffs
begin with a delete, which fails, triggering the heuristic.)
-s or --silent or --quiet
Work silently, unless an error occurs.
-t or --batch
Suppress questions like -f, but make some different assumptions: skip
patches whose headers do not contain file names (the same as -f); skip
patches for which the file has the wrong version for the Prereq: line
in the patch; and assume that patches are reversed if they look like
-T or --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. 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. Instead of
using this option, generate patches with UTC and use the -Z or
--set-utc option instead.
-u or --unified
Interpret the patch file as a unified context diff.
-v or --version
Print out patch's revision header and patch level, and exit.
-V method or --version-control=method
Use method to determine backup file names. The method can also be
given by the PATCH_VERSION_CONTROL (or, if that's not set, the
VERSION_CONTROL) environment variable, which is overridden by this
option. The method does not affect whether backup files are made; it
affects only the names of any backup files that are made.
The value of method is like the GNU Emacs `version-control' variable;
patch also recognizes synonyms that are more descriptive. The valid
values for method are (unique abbreviations are accepted):
existing or nil
Make numbered backups of files that already have them, otherwise
simple backups. This is the default.
numbered or t
Make numbered backups. The numbered backup file name for F is
F.~N~ where N is the version number.
simple or never
Make simple backups. The -B or --prefix, -Y or --basename-prefix,
and -z or --suffix options specify the simple backup file name. If
none of these options are given, then a simple backup suffix is
used; it is the value of the SIMPLE_BACKUP_SUFFIX environment
variable if set, and is .orig otherwise.
With numbered or simple backups, if the backup file name is too long,
the backup suffix ~ is used instead; if even appending ~ would make
the name too long, then ~ replaces the last character of the file
Output extra information about the work being done.
-x num or --debug=num
Set internal debugging flags of interest only to patch patchers.
-Y pref or --basename-prefix=pref
Prefix pref to the basename of a file name when generating its simple
backup file name. For example, with -Y .del/ the simple backup file
name for src/patch/util.c is src/patch/.del/util.c.
-z suffix or --suffix=suffix
Use suffix as the simple backup suffix. For example, with -z - the
simple backup file name for src/patch/util.c is src/patch/util.c-.
The backup suffix may also be specified by the SIMPLE_BACKUP_SUFFIX
environment variable, which is overridden by this option.
-Z or --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 Coordinated Universal Time (UTC, often known as GMT).
Also see the -T or --set-time option.
The -Z or --set-utc and -T or --set-time options normally refrain from
setting a file's time if the file's original time does not match the
time given in the patch header, or if its contents do not match the
patch exactly. However, if the -f or --force option is given, the
file time is set regardless.
Due to the limitations of diff output format, these options cannot
update the times of files whose contents have not changed. Also, if
you use these options, you should 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.
This specifies whether patch gets missing or read-only files from RCS,
ClearCase, Perforce, or SCCS by default; see the -g or --get option.
If set, patch conforms more strictly to the POSIX standard by default:
see the --posix option.
Default value of the --quoting-style option.
Extension to use for simple backup file names instead of .orig.
TMPDIR, TMP, TEMP
Directory to put temporary files in; patch uses the first environment
variable in this list that is set. If none are set, the default is
system-dependent; it is normally /tmp on Unix hosts.
VERSION_CONTROL or PATCH_VERSION_CONTROL
Selects version control style; see the -v or --version-control option.
controlling terminal; used to get answers to questions asked of the
Marshall T. Rose and Einar A. Stefferud, Proposed Standard for Message
Encapsulation, Internet RFC 934 <URL:ftp://ftp.isi.edu/in-
NOTES FOR PATCH SENDERS
There are several things you should bear in mind if you are going to be
sending out patches.
Create your patch systematically. A good method is 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
diff command's headers should have dates and times in Universal Time
using traditional Unix format, so that patch recipients can use the -Z or
--set-utc option. Here is an example command, using Bourne shell syntax:
LC_ALL=C TZ=UTC0 diff -Naur gcc-2.7 gcc-2.8
Tell your recipients how to apply the patch by telling them which
directory to cd to, and which patch options to use. The option string
-Np1 is recommended. Test your procedure by pretending to be a recipient
and applying your patch to a copy of the original files.
You can save people a lot of grief by keeping a patchlevel.h file which
is patched to increment the patch level as the first diff in the patch
file you send out. If you put a Prereq: line in with the patch, it won't
let them apply patches out of order without some warning.
You can create a file by sending out a diff that compares /dev/null or an
empty file dated the Epoch (1970-01-01 00:00:00 UTC) to the file you want
to create. This only works if the file you want to create doesn't exist
already in the target directory. Conversely, you can remove a file by
sending out a context diff that compares the file to be deleted with an
empty file dated the Epoch. The file will be removed unless patch is
conforming to POSIX and the -E or --remove-empty-files option is not
given. An easy way to generate patches that create and remove files is
to use GNU diff's -N or --new-file option.
If the recipient is supposed to use the -pN option, do not send output
that looks like this:
diff -Naur v2.0.29/prog/README prog/README
--- v2.0.29/prog/README Mon Mar 10 15:13:12 1997
+++ prog/README Mon Mar 17 14:58:22 1997
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 Mon Mar 10 15:13:12 1997
+++ v2.0.30/prog/README Mon Mar 17 14:58:22 1997
Avoid sending patches that compare backup file names like README.orig,
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.
Take care not to send out reversed patches, since it makes people wonder
whether they already applied the patch.
Try not to have your patch modify derived files (e.g. the file configure
where there is a line configure: configure.in in your makefile), since
the recipient should be able to regenerate the derived files anyway. If
you must send diffs of derived files, generate the diffs using UTC, have
the recipients apply the patch with the -Z or --set-utc option, and have
them remove any unpatched files that depend on patched files (e.g. with
While you may be able to get away with putting 582 diff listings into one
file, it may be wiser to group related patches into separate files in
case something goes haywire.
Diagnostics generally indicate that patch couldn't parse your patch file.
If the --verbose option is given, the message Hmm... indicates that there
is unprocessed text in the patch file and that patch is attempting to
intuit whether there is a patch in that text and, if so, what kind of
patch it is.
patch's exit status is 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 it behooves you to check this exit
status so you don't apply a later patch to a partially patched file.
Context diffs cannot reliably represent the creation or deletion of empty
files, empty directories, or special files such as symbolic links. Nor
can they represent changes to file metadata like ownership, permissions,
or whether one file is a hard link to another. If changes like these are
also required, separate instructions (e.g. a shell script) to accomplish
them should accompany the patch.
patch cannot tell if the line numbers are off in an ed script, and can
detect bad line numbers in a normal diff only when it finds a change or
deletion. A context diff using fuzz factor 3 may have the same problem.
Until a suitable interactive interface is added, you should probably do a
context diff in these cases to see if the changes made sense. Of course,
compiling without errors is a pretty good indication that the patch
worked, but not always.
patch usually produces the correct results, even when it has to do a lot
of guessing. However, the results are guaranteed to be correct only when
the patch is applied to exactly the same version of the file that the
patch was generated from.
The POSIX standard specifies behavior that differs from patch's
traditional behavior. You should be aware of these differences if you
must interoperate with patch versions 2.1 and earlier, which do not
conform to POSIX.
• 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
• In traditional patch, backups were enabled by default. This behavior
is now enabled with the -b or --backup option.
Conversely, in POSIX patch, backups are never made, even when there is
a mismatch. In GNU patch, this behavior is enabled with the
--no-backup-if-mismatch option, or by conforming to POSIX with the
--posix option or by setting the POSIXLY_CORRECT environment variable.
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
• 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
• 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.
Please report bugs via email to <email@example.com>.
patch could be smarter about partial matches, excessively deviant offsets
and swapped code, but that would take an extra pass.
If code has been duplicated (for instance with #ifdef OLDCODE ... #else
... #endif), patch is incapable of patching both versions, and, if it
works at all, will likely patch the wrong one, and tell you that it
succeeded to boot.
If you apply a patch you've already applied, patch thinks it is a
reversed patch, and offers to un-apply the patch. This could be
construed as a feature.
Copyright (C) 1984, 1985, 1986, 1988 Larry Wall.
Copyright (C) 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
1999, 2000, 2001, 2002 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be included in translations
approved by the copyright holders instead of in the original English.
Larry Wall wrote the original version of patch. Paul Eggert removed
patch's arbitrary limits; added support for binary files, setting file
times, and deleting files; and made it conform better to POSIX. Other
contributors include Wayne Davison, who added unidiff support, and David
MacKenzie, who added configuration and backup support.
GNU 2003/05/08 PATCH(1)