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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 pro-
       duced  by the diff program and applies those differences to one or more
       original files, producing patched versions.  Normally the patched  ver-
       sions  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  usu-
       ally  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  con-
       taining  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 an-
       other 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 apply-
       ing 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  speci-
       fied  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 con-
       taining 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.  See the -V or --version-con-
          trol 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  trans-
          form  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  ap-
          plied.  Normally this option is unnecessary, since patch can examine
          the time stamps on the header to determine whether a file should ex-
          ist  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 con-
          text.

       -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 de-
          fault 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 environ-
          ment 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 stan-
          dard 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 orig-
          inal  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  op-
          tion 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  adja-
          cent  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  metacharac-
                 ters 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 vari-
          able 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  na-
          ture being what it is.)  patch attempts to swap each hunk around be-
          fore  applying  it.  Rejects come out in the swapped format.  The -R
          option does not work with ed diff scripts because there is too  lit-
          tle 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  re-
          versed 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 uni-
          fied).  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 ver-
          sions 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-sav-
          ing  time  adjustments.   Make  sure  that  time stamps include time
          zones, or generate patches with UTC and use the -Z or --set-utc  op-
          tion 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  VER-
          SION_CONTROL)  environment variable, which is overridden by this op-
          tion.  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' vari-
          able; 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-pre-
             fix,  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 envi-
             ronment 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 Univer-
          sal 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 de-
          fault: 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  environ-
          ment  variable  in  this list that is set.  If none are set, the de-
          fault 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  op-
          tion.

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 directo-
       ries.  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 syn-
       tax:

              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  di-
       rectory  to  cd  to, and which patch options to use.  The option string
       -Np1 is recommended.  Test your procedure by pretending to be a recipi-
       ent 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  dif-
       ferent  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 won-
       der whether they already applied the patch.

       Try not to have your patch modify derived files (e.g. the file  config-
       ure  where  there  is a line configure: configure.in in your makefile),
       since the recipient should be able to regenerate the derived files any-
       way.  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  op-
       tion,  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  attempt-
       ing  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  prob-
       lem.   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  tradi-
       tional  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 compatibil-
          ity, 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  behav-
          ior 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  vari-
          able.

          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 bet-
          ter 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 identi-
          cal 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 ques-
          tion 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  re-
       versed  patch,  and  offers  to un-apply the patch.  This could be con-
       strued 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 en-
       tire resulting derived work is distributed under the terms of a permis-
       sion notice identical to this one.

       Permission  is granted to copy and distribute translations of this man-
       ual into another language, under the above conditions for modified ver-
       sions, except that this permission notice may be included  in  transla-
       tions approved by the copyright holders instead of in the original Eng-
       lish.

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)

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