Manual Pages  — PATCH

patch will attempt to determine the type of the diff listing, unless overruled by a -c, -e, -n, or -u option. Context diffs (old-style, new-style, and unified) and normal diffs are applied directly by the patch program itself, whereas ed diffs are simply fed to the ed(1) editor via a pipe.

If the patchfile 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 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 (see the section on Filename Determination below).

The options are as follows:

-B backup-prefix, -prefix backup-prefix Causes the next argument to be interpreted as a prefix to the backup file name. If this argument is specified, any argument to -z will be ignored.
-b -, -backup
	Save a backup copy of the file before it is modified. By default the original file is saved with a backup extension of ".orig" unless the file already has a numbered backup, in which case a numbered backup is made. This is equivalent to specifying "-V existing ". This option is currently the default, unless --posix is specified.
-C -, -check -, -dry-run
	Checks that the patch would apply cleanly, but does not modify anything.
-c -, -context
	Forces patch to interpret the patch file as a context diff.
-D symbol, -ifdef symbol Causes patch to use the "#ifdef...#endif" 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 -D and the argument.
-d directory, -directory directory Causes patch to interpret the next argument as a directory, and change the working directory to it before doing anything else.
-E -, -remove-empty-files
	Causes patch to remove output files that are empty after the patches have been applied. This option is useful when applying patches that create or remove files.
-e -, -ed
	Forces patch to interpret the patch file as an ed(1) script.
-F max-fuzz, -fuzz max-fuzz 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.
-f -, -force
	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 cannot 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.
-i patchfile, -input patchfile Causes the next argument to be interpreted as the input file name (i.e., a patchfile). This option may be specified multiple times.
-l -, -ignore-whitespace
	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.
-N -, -forward
	Causes patch to ignore patches that it thinks are reversed or already applied. See also -R.
-n -, -normal
	Forces patch to interpret the patch file as a normal diff.
-o out-file, -output out-file Causes the next argument to be interpreted as the output file name.
-p strip-count, -strip strip-count Sets the pathname strip count, which controls how pathnames 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. The strip count specifies 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 /u/howard/src/blurfl/blurfl.c: Setting -p file ... gives the entire pathname unmodified. -p 1 gives without the leading slash. -p 4 gives 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 option.
-R -, -reverse
	Tells patch that this patch was created with the old and new files swapped. (Yes, I am afraid that does happen 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 format. 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 cannot, 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.)
-r rej-name, -reject-file rej-name Causes the next argument to be interpreted as the reject file name.
-s -, -quiet, -silent Makes patch do its work silently, unless an error occurs.
-t -, -batch
	Similar to -f, in that it suppresses questions, but makes some different assumptions: skip patches for which a file to patch cannot 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.
-u -, -unified
	Forces patch to interpret the patch file as a unified context diff (a unidiff).
-V t | nil | never | none, -version-control t | nil | never | none Causes the next argument to be interpreted as a method for creating backup file names. The type of backups made can also be given in the PATCH_VERSION_CONTROL or VERSION_CONTROL environment variables, which are overridden by this option. The -B option overrides this option, causing the prefix to always be used for making backup file names. The values of the PATCH_VERSION_CONTROL and VERSION_CONTROL environment variables and the argument to the -V option are like the GNU Emacs "version-control" variable; they also recognize synonyms that are more descriptive. The valid values are (unique abbreviations are accepted):
t, numbered
	Always make numbered backups.
nil, existing
	Make numbered backups of files that already have them, simple backups of the others.
never, simple
	Always make simple backups.
none	Do not make backups.

-v -, -version
	Causes patch to print out its revision header and patch level.
-x number, -debug number Sets internal debugging flags, and is of interest only to patch patchers.
-z backup-ext, -suffix backup-ext Causes the next argument to be interpreted as the backup extension, to be used in place of ".orig".
-posix
	Enables strict IEEE Std 1003.1-2008 ("POSIX.1") conformance, specifically: Backup files are not created unless the -b option is specified. If unspecified, the file name used is the first of the old, new and index files that exists.