PATCH(1) GNU (1998/03/21) PATCH(1)
NAME
patch - apply a diff file to an original
SYNOPSIS
patch [options] [originalfile [patchfile]]
but usually just
patch-pnum <patchfile
DESCRIPTION
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.
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
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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:
o 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.
o 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.
o 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:
o If some of the named files exist, patch selects the first
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name if conforming to POSIX, and the best name otherwise.
o If patch is not ignoring RCS, ClearCase, and SCCS (see
the -g num or --get=num option), 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.
o 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.
o 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.
OPTIONS
-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
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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 patch is conforming to POSIX.
--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 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.
--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. 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 patch
is conforming to POSIX, patch does not remove empty
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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 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, 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.
--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.
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PATCH(1) GNU (1998/03/21) PATCH(1)-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.
-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
/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.
--posix
Conform more strictly to the POSIX standard, as follows.
o Take the first existing file from the list (old, new,
index) when intuiting file names from diff headers.
o Do not remove files that are empty after patching.
o Do not ask whether to get files from RCS, ClearCase,
or SCCS.
o Require that all options precede the files in the
command line.
o Do not backup files when there is a mismatch.
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--quoting-style=word
Use style word to quote output names. 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.
-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.)
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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
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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.
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ENVIRONMENT
PATCH_GET
This specifies whether patch gets missing or read-only
files from RCS, ClearCase, or SCCS by default; see the -g
or --get option.
POSIXLY_CORRECT
If set, patch conforms more strictly to the POSIX
standard by default: see the --posix option.
QUOTING_STYLE
Default value of the --quoting-style option.
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.
FILES
$TMPDIR/p*
temporary files
/dev/tty
controlling terminal; used to get answers to questions
asked of the user
SEE ALSO
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).
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
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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.
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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
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.
CAVEATS
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
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guaranteed to be correct only when the patch is applied to
exactly the same version of the file that the patch was
generated from.
COMPATIBILITY ISSUES
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.
o 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.
o 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.
o 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.
o 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
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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.
o 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.
o 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
BUGS
Please report bugs via email to <bug-gnu-utils@gnu.org>.
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.
COPYING
Copyright 1984, 1985, 1986, 1988 Larry Wall.
Copyright 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
1997, 1998 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.
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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.
AUTHORS
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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