PATCH(1) USER COMMANDS PATCH(1)
patch - apply a diff file to an original
patch [options] [origfile [patchfile]] [+ [options] [orig
but usually just
Patch will take a patch file containing any of the four
forms of difference listing produced by the diff program and
apply those differences to an original file, producing a
patched version. By default, the patched version is put in
place of the original, with the original file backed up to
the same name with the extension ".orig" ("~" on systems
that do not support long file names), or as specified by the
-b (--suffix), -B (--prefix), or -V (--version-control)
options. The extension used for making backup files may
also be specified in the SIMPLE_BACKUP_SUFFIX environment
variable, which is overridden by the above options.
If the backup file already exists, patch creates a new
backup file name by changing the first lowercase letter in
the last component of the file's name into uppercase. If
there are no more lowercase letters in the name, it removes
the first character from the name. It repeats this process
until it comes up with a backup file that does not already
You may also specify where you want the output to go with a
-o (--output) option; if that file already exists, it is
backed up first.
If patchfile is omitted, or is a hyphen, the patch will be
read from standard input.
Upon startup, patch will attempt to determine the type of
the diff listing, unless over-ruled 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 editor via a pipe.
Patch will try 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 consis
tent amount, this will be 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 will attempt to find the cor
rect 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 will scan 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 will put the
hunk out to a reject file, which normally is the name of the
output file plus ".rej" ("#" on systems that do not support
long file names). (Note that the rejected hunk will come
out in context diff form whether the input patch was a con
text diff or a normal diff. If the input was a normal diff,
many of the contexts will simply be 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 will be told whether the hunk
succeeded or failed, and which line (in the new file) patch
thought the hunk should go on. If this is different from
the line number specified in the diff you will be told the
offset. A single large offset MAY be an indication that a
hunk was installed in the wrong place. You will also be
told if a fuzz factor was used to make the match, in which
case you should also be slightly suspicious.
If no original file is specified on the command line, patch
will try to figure out from the leading garbage what the
name of the file to edit is. In the header of a context
diff, the file name is found from lines beginning with "***"
or "---", with the shortest name of an existing file win
ning. Only context diffs have lines like that, but if there
is an "Index:" line in the leading garbage, patch will try
to use the file name from that line. The context diff
header takes precedence over an Index line. If no file name
can be intuited from the leading garbage, you will be asked
for the name of the file to patch.
If the original file cannot be found or is read-only, but a
suitable SCCS or RCS file is handy, patch will attempt to
get or check out the file.
Additionally, if the leading garbage contains a "Prereq: "
line, patch will take the first word from the prerequisites
line (normally a version number) and check the input file to
see if that word can be found. If not, patch will ask for
confirmation before proceeding.
The upshot of all this is that you should be able to say,
while in a news interface, 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 will
try 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 deter
mined for each diff listing, and that the garbage before
each diff listing will be examined for interesting things
such as file names and revision level, as mentioned previ
ously. You can give options (and another original file
name) for the second and subsequent patches by separating
the corresponding argument lists by a '+'. (The argument
list for a second or subsequent patch may not specify a new
patch file, however.)
Patch recognizes the following options:
-b suff, --suffix=suff
causes suff to be interpreted as the backup extension,
to be used in place of ".orig" or "~".
-B pref, --prefix=pref
causes pref to be interpreted as a prefix to the backup
file name. If this argument is specified, any argument
from -b will be ignored.
forces patch to interpret the patch file as a context
-d dir, --directory=dir
causes patch to interpret dir as a directory, and cd to
it before doing anything else.
-D sym, --ifdef=sym
causes patch to use the "#ifdef...#endif" construct to
mark changes. sym will be used as the differentiating
forces patch to interpret the patch file as an ed
causes patch to remove output files that are empty
after the patches have been applied.
forces patch to assume that the user knows exactly what
he or she is doing, and to not ask any questions. It
assumes the following: skip patches for which a file to
patch can't be found; 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.
similar to -f, in that it suppresses questions, but
makes some different assumptions: skip patches for
which a file to patch can't be found (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.
-F number, --fuzz=number
sets the maximum fuzz factor. This option only applies
to context diffs, 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.
causes the pattern matching to be done loosely, in case
the tabs and spaces have been munged in your input
file. Any sequence of whitespace in the pattern line
will match any sequence in the input file. Normal
characters must still match exactly. Each line of the
context must still match a line in the input file.
forces patch to interpret the patch file as a normal
causes patch to ignore patches that it thinks are
reversed or already applied. See also -R .
-o file, --output=file
causes file to be interpreted as the output file name.
sets the pathname strip count, which controls how path
names found in the patch file are treated, in case the
you keep your files in a different directory than the
person who sent out the patch. The strip count speci
fies how many slashes are to be stripped from the front
of the pathname. (Any intervening directory names also
go away.) For example, supposing the file name in the
patch file was
setting -p or -p0 gives the entire pathname unmodified,
without the leading slash, -p4 gives
and not specifying -p at all just gives you "blurfl.c",
unless all of the directories in the leading path
(u/howard/src/blurfl) exist and that path is relative,
in which case you get the entire pathname unmodified.
Whatever you end up with is looked for either in the
current directory, or the directory specified by the -d
-r file, --reject-file=file
causes file to be interpreted as the reject file name.
tells patch that this patch was created with the old
and new files swapped. (Yes, I'm afraid that does hap
pen occasionally, human nature being what it is.)
Patch will attempt to swap each hunk around before
applying it. Rejects will come out in the swapped for
mat. The -R option will 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 will reverse
the hunk to see if it can be applied that way. If it
can, you will be asked if you want to have the -R
option set. If it can't, the patch will continue 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 will match anywhere. Luckily, most
patches add or change lines rather than delete them, so
most reversed normal diffs will begin with a delete,
which will fail, triggering the heuristic.)
-s, --silent, --quiet
makes patch do its work silently, unless an error
causes patch to ignore this patch from the patch file,
but continue on looking for the next patch in the file.
patch -S + -S + <patchfile
will ignore the first and second of three patches.
forces patch to interpret the patch file as a unified
context diff (a unidiff).
causes patch to print out its revision header and patch
-V method, --version--control=method
causes method to be interpreted as a method for creat
ing backup file names. The type of backups made can
also be given in the VERSION_CONTROL environment vari
able, which is overridden by this option. The -B
option overrides this option, causing the prefix to
always be used for making backup file names. The value
of the VERSION_CONTROL environment variable and the
argument to the -V option are like the GNU Emacs `ver
sion-control' variable; they also recognize synonyms
that are more descriptive. The valid values are
(unique abbreviations are accepted):
`t' or `numbered'
Always make numbered backups.
`nil' or `existing'
Make numbered backups of files that already have
them, simple backups of the others. This is the
`never' or `simple'
Always make simple backups.
-x number, --debug=number
sets internal debugging flags, and is of interest only
to patch patchers.
Larry Wall <email@example.com>
with many other contributors.
Directory to put temporary files in; default is /tmp.
Extension to use for backup file names instead of
".orig" or "~".
Selects when numbered backup files are made.
NOTES FOR PATCH SENDERS
There are several things you should bear in mind if you are
going to be sending out patches. First, 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. Second, make sure you've specified
the file names right, either in a context diff header, or
with an Index: line. If you are patching something in a
subdirectory, be sure to tell the patch user to specify a -p
option as needed. Third, you can create a file by sending
out a diff that compares a null file to the file you want to
create. This will only work if the file you want to create
doesn't exist already in the target directory. Fourth, take
care not to send out reversed patches, since it makes people
wonder whether they already applied the patch. Fifth, while
you may be able to get away with putting 582 diff listings
into one file, it is probably wiser to group related patches
into separate files in case something goes haywire.
Too many to list here, but generally indicative that patch
couldn't parse your patch file.
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 will exit with a non-zero status if any reject files
were created. 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.
Patch cannot tell if the line numbers are off in an ed
script, and can only detect bad line numbers in a normal
diff when it finds a "change" or a "delete" command. A con
text 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
Patch usually produces the correct results, even when it has
to do a lot of guessing. However, the results are guaran
teed to be correct only when the patch is applied to exactly
the same version of the file that the patch was generated
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 OLD
CODE ... #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 will
think it is a reversed patch, and offer to un-apply the
patch. This could be construed as a feature.
Sun Release 4.1 Last change: LOCAL 1