patch

PATCH(1)                     General Commands Manual                    PATCH(1)



NAME
       patch - apply a diff file to an original

SYNOPSIS
       patch [options] [originalfile [patchfile]]

       but usually just

       patch -pnum <patchfile

DESCRIPTION
       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 name.

       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.

OPTIONS
       -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 determined.

       --backup-if-mismatch
          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.

       --no-backup-if-mismatch
          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
          /junk/src/patch/util.c.

       --binary
          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.

       --dry-run
          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
          context.

       -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.

       --help
          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

          /u/howard/src/blurfl/blurfl.c

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

          u/howard/src/blurfl/blurfl.c

       without the leading slash, -p4 gives

          blurfl/blurfl.c

       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.

       --posix
          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
             SCCS.

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

           Do not backup files when there is a mismatch.

       --quoting-style=word
          Use style word to quote output names.  The word should be one of the
          following:

          literal
                 Output names as-is.

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

          shell-always
                 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
                 characters.

          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.)

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

       --reject-format=format
          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.

       --follow-symlinks
          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 otherwise.

          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.

       --verbose
          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.

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

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

       QUOTING_STYLE
          Default value of the --quoting-style option.

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

       TMPDIR, TMP, TEMP
          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.

       VERSION_CONTROL or PATCH_VERSION_CONTROL
          Selects version control style; see the -v or --version-control option.

FILES
       $TMPDIR/p*
          temporary files

       /dev/tty
          controlling terminal; used to get answers to questions asked of the
          user

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

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

NOTES FOR PATCH SENDERS
       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: configure.in 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
       Diagnostics generally indicate that patch couldn't parse your patch file.

       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.

CAVEATS
       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.

COMPATIBILITY ISSUES
       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
          names.

        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 variable.

          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.

             -c
             -d dir
             -D define
             -e
             -l
             -n
             -N
             -o outfile
             -pnum
             -R
             -r rejectfile

BUGS
       Please report bugs via email to <bug-patch@gnu.org>.

       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
       down.

COPYING
       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.

AUTHORS
       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)