Table of Contents
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 is encapsulated one or more times by prepending
"- " to lines starting with "- " as specified by Internet RFC 934, this
is taken into account.
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.
- · If the header is that of a context diff,
- patch takes the old and new
file names in the header. Any /dev/null names are ignored.
- · If there is
an
- Index: line in the leading garbage and if either the old and new names
are both absent or the POSIXLY_CORRECT environment variable is set, patch
takes the name in the Index: line.
- · For the purpose of the following rules,
- the names are considered to be in the order (old, new, index), regardless
of the order that they appear in the header.
- · If some of the named files
exist,
- patch uses the first name if the POSIXLY_CORRECT environment variable
is set, and the best name otherwise.
- · If
- patch is not ignoring RCS
and
SCCS
(see the -g num or get=num option), and no named files exist but an
RCS
or SCCS
master is found, patch uses the first named file with an RCS
or SCCS
master.
- · If no named files exist, no RCS or SCCS master was found,
- some names are given, POSIXLY_CORRECT is not set, and the patch appears
to create a file, patch uses 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.
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.
- backup-if-mismatch
- 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 the POSIXLY_CORRECT environment variable
is set.
- no-backup-if-mismatch
- 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 the POSIXLY_CORRECT environment variable is set.
- -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.
- binary
- Read and write all
files in binary mode, except for standard output and /dev/tty. This option
has no effect on POSIX
-compliant 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.
- dry-run
- Print the results of applying the patches without actually
changing any files.
- -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 the POSIXLY_CORRECT environment variable is set, 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. If num
is positive, patch gets (or checks out) the file from the revision control
system; if zero, patch ignores RCS
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 POSIXLY_CORRECT
is set, negative otherwise.
- help
- 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 original file.
- -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 -R.
- -o outfile or
output= outfile
- Send output to outfile instead of patching files in
place.
- -p num 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
/u/howard/src/blurfl/blurfl.c
setting -p0 gives the entire file name unmodified, -p1 gives
u/howard/src/blurfl/blurfl.c
without the leading slash, -p4 gives
blurfl/blurfl.c
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.
- -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 they are.
- -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 name.
- verbose
- 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.
- PATCH_GET
- This specifies whether
patch gets missing or read-only files from RCS
or SCCS
by default; see
the -g or get option.
- POSIXLY_CORRECT
- If set, patch conforms more strictly
to the POSIX
standard: it takes the first existing file from the list
(old, new, index) when intuiting file names from diff headers, it does
not remove files that are empty after patching, it does not ask whether
to get files from RCS
or SCCS
, it requires that all options precede the
files in the command line, and it does not backup files when there is
a mismatch.
- SIMPLE_BACKUP_SUFFIX
- 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.
- $TMPDIR/p*
- temporary files
- /dev/tty
- controlling terminal; used to get answers to
questions asked of the user
diff(1)
, ed(1)
Marshall T. Rose
and Einar A. Stefferud, Proposed Standard for Message Encapsulation, Internet
RFC 934 <URL:ftp://ftp.isi.edu/in-notes/rfc934.txt> (1985-01).
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 the POSIXLY_CORRECT environment
variable is set 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 make clean).
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 are not POSIX
-compliant.
- · In traditional
- patch, the -p option's operand
was optional, and a bare -p was equivalent to -p0. The -p option now requires
an operand, and -p 0 is now equivalent to -p0. For maximum compatibility,
use options like -p0 and -p1.
Also, traditional patch simply counted slashes
when stripping path prefixes; patch now counts pathname components. That
is, a sequence of one or more adjacent slashes now counts as a single
slash. For maximum portability, avoid sending patches containing // in
file names.
- · In traditional
- patch, backups were enabled by default. This
behavior is now enabled with the -b or backup option.
Conversely, in
POSIX
patch, backups are never made, even when there is a mismatch. In
GNU
patch, this behavior is enabled with the no-backup-if-mismatch option
or by 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 was not POSIX
-compliant, and had a few gotchas. Now patch uses
a different, equally complicated (but better documented) method that is
optionally POSIX
-compliant; 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 POSIX
-compliant patch.
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
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
1984, 1985, 1986, 1988 Larry Wall.
Copyright 1997 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.
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