patch(1)patch(1)NAMEpatch - program to apply a diff file to an original file
SYNOPSIS
[options] orig patchfile options] orig]
UNIX Standard Version
dir] define] patchfile] outfile] num] rejectfile] [file]
DESCRIPTION
will take a patch file containing any of the three forms of difference
listing produced by the program (normal, context or in the style of and
apply those differences to an original file, producing a patched ver‐
sion. 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 or
as specified by the option. Note that functionality of this option
varies for the UNIX Standard version (see standards(5)). You may also
specify where you want the output to go with a option. If patchfile is
omitted, or is a hyphen, the patch will be read from standard input.
For the UNIX Standard (see standards(5)) version, patchfile has to be
specified as argument to the option. If this option is omitted or a
hyphen is specified as argument, the patch will read from standard
input.
Upon startup, patch will attempt to determine the type of the diff
listing, unless overruled by a or option. Context diffs and normal
diffs are applied by the program itself, while diffs are simply fed to
the editor via a pipe.
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 and it should work. If the entire diff is indented
by a consistent amount, this will be taken into account.
With context diffs, and to a lesser extent with normal diffs, can
detect when the line numbers mentioned in the patch are incorrect, and
will attempt 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, will scan both forwards and backwards for a set of
lines matching the context given in the hunk. First, looks for a place
where all lines of the context match. If no such place is found, and
it is 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 con‐
text. 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.) Note that for
the UNIX Standard (see standards(5)) version, the maximum fuzz factor
can not be specified as an option, and the default maximum fuzz factor
is used. If 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 (Note that the rejected hunk will come out in con‐
text diff form whether the input patch was a context 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 dif‐
ferent 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) 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 indica‐
tion 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. Note that the UNIX standard (see
standards(5)) version does not support verbose option. So, most of the
diagnostic messages are not printed for this version. However user
queries will always be displayed.
If no original file is specified on the command line, will try to fig‐
ure 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 winning.
Only context diffs have lines like that, but if there is an line in the
leading garbage, 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, but a suitable SCCS or RCS file
is handy, will attempt to get or check out the file.)
Additionally, if the leading garbage contains a line, 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, 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:
and patch a file in the directory directly from the article containing
the patch.
If the patch file contains more than one 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 determined 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 previously. You can give
options (and another original file name) for the second and subsequent
patches by separating the corresponding argument lists by a (The argu‐
ment list for a second or subsequent patch may not specify a new patch
file, however.)
With the UNIX Standard (see standards(5)) version, processing of multi‐
ple patches varies considerably. You can not specify different options
for different patches. Options remain same for all the patches. This
also affects the contents of output file specified with the option.
See the description of this option for more details.
Options
recognizes the following options:
causes the next argument to be interpreted as the backup extension, to
be
used in place of (For the UNIX Standard (see standards(5)) ver‐
sion, this option varies. With this option, no argument is
required and the option only enables the backup process. The
default extension is always used.)
forces
to interpret the patch file as a context diff.
causes
to interpret the next argument as a directory, and to it before
doing anything else.
causes
to use the construct to mark changes. The argument following will
be used as the differentiating symbol. Note that, unlike the C
compiler, there must be a space between the and the argument.
(For the UNIX Standard (see standards(5)) version, this option
varies. With this version, the constructor is not used.)
forces
to interpret the patch file as an script.
forces
to assume that the user knows exactly what he or she is doing, and
to not ask any questions. It does not suppress commentary, how‐
ever. Use for that. This option is not supported by the UNIX
Standard version.
sets the maximum fuzz factor.
This option only applied to context diffs, and causes 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.
This option is not supported by the UNIX Standard version.
This option is supported only by the UNIX Standard version.
See standards(5)) for information about the UNIX standard environ‐
ment. It causes next argument to be interpreted as the patch file
name.
causes the pattern matching to be done loosely, in case the tabs and
spaces have been munged in your input file. Any sequence of white
space 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
to interpret the patch file as a normal diff.
causes
to ignore patches that it thinks are reversed or already applied.
See also
causes the next argument to be interpreted as the output file name.
There are some added features for the UNIX Standard version. For
information about the UNIX standard environment, see standards(5).
Multiple patches for a single file will be applied to the interme‐
diate versions of the file created by any previous patches, and
will result in multiple,concatenated versions of the file being
written to output file.
sets the path name 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 specifies how many
backslashes are to be stripped from the front of the path name.
(Any intervening directory names also go away.) For example, sup‐
posing the file name in the patch file was
setting or gives the entire path name unmodified, gives
without the leading slash, gives
and not specifying at all just gives you Whatever you end up with
is looked for either in the current directory, or the directory
specified by the option.
causes the next argument to be interpreted as the reject file name.
informs
that this patch was created with the old and new files swapped.
will attempt to swap each hunk around before applying it. Rejects
will come out in the swapped format. The option will not work
with diff scripts because there is too little information to
reconstruct the reverse operation.
If the first hunk of a patch fails, 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 option set. If it can not, 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 (that is, it should have been a delete) since appends
always succeed, due to the fact that a null context will match
anywhere. 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.)
makes
do its work silently, unless an error occurs. This option is not
supported by the UNIX Standard version.
causes
to ignore this patch from the patch file, but continue on looking
for the next patch in the file. Thus
will ignore the first and second of three patches. This option is
not supported by the UNIX Standard version.
causes
to print out its revision header and patch level. This option is
not supported by the UNIX Standard version.
sets internal debugging flags, and is of interest only to
patchers. This option is not supported by the UNIX Standard ver‐
sion.
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 file which is patched to increment the patch level as the
first diff in the patch file you send out. If you put a line in with
the patch, it will not let them apply patches out of order without some
warning. Second, make sure you have specified the file names right,
either in a context diff header, or with an line. If you are patching
something in a subdirectory, be sure to tell the patch user to specify
a 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 does not 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 sepa‐
rate files in case something goes haywire.
RETURN VALUE
The following exit values are returned for the UNIX Standard (see stan‐
dards(5)) version:
Successful completion.
One or more lines were written to a reject file.
An error occurred.
For the non-UNIX Standard version, exit values vary as follows:
Successful completion or one or more lines were written to a
reject file.
An error occurred.
DIAGNOSTICS
Most error messages indicate that could not parse your patch file.
The message indicates that there is unprocessed text in the patch file
and that is attempting to intuit whether there is a patch in that text
and, if so, what kind of patch it is.
Note that only few diagnostic messages are printed for the UNIX Stan‐
dard version, because it does not support the verbose option.
WARNINGS
cannot tell if the line numbers are off in an script, and can only
detect bad line numbers in a normal diff when it finds a change or a
delete command. 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.
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 result obtained from the UNIX Standard options and which force the
patch command to interpret the diff file either as a context diff or as
an script or as a normal diff respectively, is unspecified. For exam‐
ple, if one forces the patch command to treat the context diff file as
an script, the result is unspecified. The same is true if one forces
patch to treat an script as a context file and so on.. When a diff is
forced with the above options, the diff file is searched for patterns
that are specific to that type of diff file. If the diff file is not
what was specified by the option, the file is checked for commands. If
commands are present in the diff file, then the file is assumed to be
an file and the patch proceeds.
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 is incapable of patching
both versions, and, if it works at all, will likely patch the wrong
one, and tell you that it succeeded.
If you apply a patch that you have already applied, will think it is a
reversed patch, and offer to un-apply the patch. This could be con‐
strued as a feature.
UNIX Standard version: If you are using multiple patches for different
files, group patches that have to be applied to a single file. Other‐
wise, intermediate versions of the previous patches of a file will not
be used for the current patch.
FILESSEE ALSOdiff(1), ed(1), standards(5).
STANDARDS CONFORMANCEpatch(1)
