PATCH(1)                    General Commands Manual                   PATCH(1)

       patch - apply a diff file to an original

       patch [options] [originalfile [patchfile]]

       but usually just

       patch -pnum <patchfile

       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 be 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, if lines end in CRLF, or if a
       diff is encapsulated one or more times by prepending "- " to lines
       starting with "-" as specified by Internet RFC 934, this is taken into
       account.  After removing indenting or encapsulation, lines beginning
       with # are ignored, as they are considered to be comments.

       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 default maximum fuzz factor is 2.)

       Hunks with less prefix context than suffix context (after applying
       fuzz) must apply at the start of the file if their first line number
       is 1.  Hunks with more prefix context than suffix context (after
       applying fuzz) must apply at the end of the file.

       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 unified or context diff format.  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:

        · 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.

        · 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.

        · 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:

        · If some of the named files exist, patch selects the first name if
          conforming to POSIX, and the best name otherwise.

        · If patch is not ignoring RCS, ClearCase, Perforce, and SCCS (see the
          -g num or --get=num option), and no named files exist but an RCS,
          ClearCase, Perforce, or SCCS master is found, patch selects the
          first named file with an RCS, ClearCase, Perforce, or SCCS master.

        · If no named files exist, no RCS, ClearCase, Perforce, 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.

        · 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

       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.

       -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 represent the nonexistent file.  See the -V or
          --version-control option for details about how backup file names are

          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.

          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
          Use the simple method to determine backup file names (see the -V
          method or --version-control method option), and append pref to a
          file name when generating its backup file name.  For example, with
          -B /junk/ the simple backup file name for src/patch/util.c is

          Write all files in binary mode, except for standard output and
          /dev/tty.  When reading, disable the heuristic for transforming CRLF
          line endings into LF line endings.  This option is needed on POSIX
          systems when applying patches generated on non-POSIX systems to non-
          POSIX files.  (On POSIX systems, file reads and writes never
          transform line endings. On Windows, reads and writes do transform
          line endings by default, and patches should be generated by
          diff --binary when line endings are significant.)

       -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.

          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
          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 of
          context 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.  A fuzz factor greater than or equal to the number of
          lines of context in the context diff, ordinarily 3, ignores all

       -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 or Perforce
          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, Perforce, 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.

          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.

       --merge or --merge=merge or --merge=diff3
          Merge a patch file into the original files similar to diff3(1) or
          merge(1).  If a conflict is found, patch outputs a warning and
          brackets the conflict with <<<<<<< and >>>>>>> lines.  A typical
          conflict will look like this:

              lines from the original file
              original lines from the patch
              new lines from the patch

          The optional argument of --merge determines the output format for
          conflicts: the diff3 format shows the ||||||| section with the
          original lines from the patch; in the merge format, this section is
          missing.  The merge format is the default.

          This option implies --forward and does not take the --fuzz=num
          option into account.

       -n  or  --normal
          Interpret the patch file as a normal diff.

       -N  or  --forward
          When a patch does not apply, patch usually checks if the patch looks
          like it has been applied already by trying to reverse-apply the
          first hunk.  The --forward option prevents that.  See also -R.

       -o outfile  or  --output=outfile
          Send output to outfile instead of patching files in place.  Do not
          use this option if outfile is one of the files to be patched.  When
          outfile is -, send output to standard output, and send any messages
          that would usually go to standard output to standard error.

       -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


       setting -p0 gives the entire file name unmodified, -p1 gives


       without the leading slash, -p4 gives


       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.

          Conform more strictly to the POSIX standard, as follows.

           · Take the first existing file from the list (old, new, index) when
             intuiting file names from diff headers.

           · Do not remove files that are empty after patching.

           · Do not ask whether to get files from RCS, ClearCase, Perforce, or

           · Require that all options precede the files in the command line.

           · Do not backup files when there is a mismatch.

          Use style word to quote output names.  The word should be one of the

                 Output names as-is.

          shell  Quote names for the shell if they contain shell
                 metacharacters or would cause ambiguous output.

                 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

          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.  When
          rejectfile is -, discard rejects.

       -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.)

          Behave as requested when trying to modify a read-only file: ignore
          the potential problem, warn about it (the default), or fail.

          Produce reject files in the specified format (either context or
          unified).  Without this option, rejected hunks come out in unified
          diff format if the input patch was of that format, otherwise in
          ordinary context diff form.

       -s  or  --silent  or  --quiet
          Work silently, unless an error occurs.

          When looking for input files, follow symbolic links.  Replaces the
          symbolic links, instead of modifying the files the symbolic links
          point to.  Git-style patches to symbolic links will no longer apply.
          This option exists for backwards compatibility with previous
          versions of patch; its use is discouraged.

       -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.  Unless specified in the time
          stamps, assume that the context diff headers use local time.

          Use of this option with time stamps that do not include time zones
          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.  Make sure that time stamps include time
          zones, or 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
             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

          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.

          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
          Use the simple method to determine backup file names (see the -V
          method or --version-control method option), and prefix pref to the
          basename of a file name when generating its 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 the simple method to determine backup file names (see the -V
          method or --version-control method option), and use suffix as the
          suffix.  For example, with -z - the backup file name for
          src/patch/util.c is src/patch/util.c-.

       -Z  or  --set-utc
          Set the modification and access times of patched files from time
          stamps given in context diff headers. Unless specified in the time
          stamps, assume 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.

          This specifies whether patch gets missing or read-only files from
          RCS, ClearCase, Perforce, or SCCS by default; see the -g or --get

          If set, patch conforms more strictly to the POSIX standard by
          default: see the --posix option.

          Default value of the --quoting-style option.

          Extension to use for simple backup file names instead of .orig.

          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.

          Selects version control style; see the -v or --version-control

          temporary files

          controlling terminal; used to get answers to questions asked of the

       diff(1), ed(1), merge(1).

       Marshall T. Rose and Einar A. Stefferud, Proposed Standard for Message
       Encapsulation, Internet RFC 934 <URL:
       notes/rfc934.txt> (1985-01).

       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 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.

       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: 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 generally indicate that patch couldn't parse your patch

       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 or there were merge conflicts, 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.

       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.  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 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 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.

        · 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

        · 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

          The -b suffix option of traditional patch is equivalent to the
          -b -z suffix options of GNU patch.

        · 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.

        · 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 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.

        · 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.

        · 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.

             -d dir
             -D define
             -o outfile
             -r rejectfile

       Please report bugs via email to <>.

       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.

       Computing how to merge a hunk is significantly harder than using the
       standard fuzzy algorithm.  Bigger hunks, more context, a bigger offset
       from the original location, and a worse match all slow the algorithm

       Copyright (C) 1984, 1985, 1986, 1988 Larry Wall.
       Copyright (C) 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
       1998, 1999, 2000, 2001, 2002, 2009 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.

       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.

       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.  Andreas
       Grünbacher added support for merging.

GNU                                                                   PATCH(1)