NAME
	patch - Apply patches to files

SYNOPSIS
	patch [-c | -e | -n | -u] [-d dir] [-D define] [-o outfile] [-p num]
	      [-r rejectfile] [-bflNRU] (-i patchfile | < patchfile) [file]

DESCRIPTION
	patch applies patches to files from difference listings produced by
	diff(1).

	patch will skip any garbage unless the patchfile consists entirely of
	garbage. Garbage is any data that does not conform to the supported
	difference listing formats. patch supports all difference listing
	formats specified in diff(1p) except for the -f flag in diff(1p).

	patch shall figure out which files to patch from the mentions of
	filenames in the patch, unless the files are specified explicitly.
	As an extension to the standard, this implementation of patch can
	determine the filename by looking at the diff-lines that are produced
	by diff(1) when comparing directories. However, if the file is
	specified, all patches in the patchfile shall be applied to that file.

OPTIONS
	-b
		Back up files before the first time that a patch is applied to
		them. The backups will have the suffix .orig.

	-c
		Treat anything that is not conforming to the copied context
		format as garbage.

	-d dir
		Prepend dir to all filenames that appear in the patchfile.

	-D define
		 Mark added lines with the C preprocessor construct

			#ifdef define
			...
			#endif

		Mark removed lines with the C preprocessor construct

			#ifndef define
			...
			#endif

		 Mark changed lines with the C preprocessor construct

			#ifdef define
			...
			#else
			...
			#endif

		As an extension to the standard, define can be 1 or 0 to use

			#if 1
			#if 0

		(swap those lines if define is 0) instead of

			#ifdef define
			#ifndef define

		As another extension to the standard, if define begins with an
		exclamation point (!),

			#ifdef define
			#if 1

		and

			#ifndef define
			#if 0

		are swapped.

		patch does not guarantee that a patched C source code file will
		be at least as syntactically correct after patching as it was
		before, despite this being implied by the standard. The
		syntactic correctness can be broken when edits are made on lines
		split using line continuation, made in comments, or spanning CPP
		conditional directives.

	-e
		Treat anything that is not conforming to the ed-script format as
		garbage.

	-f
		Don't ask any questions.

	-i patchfile
		Read the patchfile instead of standard output.

	-l
		Any sequence of whitespace of at least length 1 in the input
		file shall match any sequence of whitespace of at least length
		1 in the difference script when testing if lines match.
		Additionally, any whitespace at the beginning of a line or at
		the end of a line is ignored when matching lines. The former
		case is an extension of the standard.

	-n
		Treat anything that is not conforming to the normal format as
		garbage.

	-N
		Ignore already applied hunks. POSIX specifies that already
		applied patches shall be ignored if this flag is used. A hunk
		is a contiguous portion of a patch. A patch is a single
		file-comparison output from diff(1).

	-o outfile
		Store resulting files from patches to outfile instead of to
		the patched file itself. If the patchfile patches multiple
		files, the results are concatenated. If a patchfile patches a
		file multiple times, intermediary results are also stored.

		As an extension to the standard, you may use non-regular files
		such as /dev/stdout and /dev/null. /dev/null can be used
		to perform a dryrun.

	-p num
		Remove the first num components from filenames that appear in
		the patchfile. Any leading / is regarded as the first component.
		If num is 0, the entire filename is used. Without this flag only
		basename is used.

	-r rejectfile
		Save rejected hunks to rejectfile rather than to the
		filename.rej where filename is the filename of the file that is
		being patched. Rejected hunks are hunks that cannot be applied.

		Unless -U is used, rejected hunks are stored in copied context
		format. However, the timestamps will be omitted.

	-R
		Try to apply patches reversed before trying to apply them in
		normal direction.

	-u
		Treat anything that is not conforming to the unified context
		format as garbage.

	-U
		Store rejected hunks in unified context rather than copied
		context. Copied context is the default even for unified context
		patches.

NOTES
	Files that become empty as a result of a patch are not removed.

	Symbolic links are treated as regular files, provided that they link to
	regular files.

	Timestamps that appear in diff headers are not applied.

	Encapsulated patches, and patches with CRLF line breaks — or any other
	string — rather than LF line breaks are not supported.

	In this implementation, when the user is prompted, the message is
	printed to /dev/tty, rather than /dev/stdout despite POSIX's
	mandate. This is to make it possible to use /dev/stdout as the output
	file.

	Unportable characters in filenames are supported by parsing them as C
	string literals.

	In this implementation, the -D flag can be used with ed-scripts.

SEE ALSO
	diff(1), ed(1)

STANDARDS
	The patch utility is compliant with the specification except for the
	exceptions noted above.

	The [-fU] flags are extensions to that specification, other extensions
	are noted above.