patch


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, or if a context diff  contains
       lines ending in CRLF or 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  com-
       ments.

       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 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
       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:

        o 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.

        o 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.

        o 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:

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

        o 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.

        o 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.

        o 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.
       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.   (On  POSIX-conforming  systems,
          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
          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 in
          looking for places to install a hunk.  Note that a larger fuzz  fac-
          tor  increases  the odds of a faulty patch.  The default fuzz factor
          is 2, and it may not be set to more than the number of lines of con-
          text in the context diff, ordinarily 3.

       -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 con-
          trol 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  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
          Merge a patch file into the original files similar to 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
              =======
              lines from the patch
              >>>>>>>

          If  there  are conflicts, the user should edit the result and delete
          one of the alternatives.  This option implies --forward and does not
          take the --fuzz=num option into account.


       -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.

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

           o Do not remove files that are empty after patching.

           o Do not ask whether to get files from RCS, ClearCase, Perforce, or
             SCCS.

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

           o 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.

          Same  as --reject-file=rejectfile.  This option is deprecated and is
          a Debian-specific  extension  that  will  be  removed  in  a  future
          release.

       -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 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
          reversed normal diffs begin with a delete, which  fails,  triggering
          the heuristic.)

       --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.

       -U  or  --unified-reject-files
          Produce unified reject files.   This option is deprecated and  is  a
          Debian-specific  extension that will be removed in a future release.
          Use --reject-format=format instead.

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

       -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, assuming that the context diff
          headers use local time.  This option  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.
          Instead of using this option, generate patches with UTC and use  the
          -Z or --set-utc option instead.


          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, assuming 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
          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 environ-
          ment 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 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
       directory  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.
       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
       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 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.
       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.

        o In  traditional  patch,  the -p option's operand was optional, and a
          bare -p was equivalent to -p0.  The -p option now requires an  oper-
          and,  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.

        o 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.

        o 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.

        o 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
             -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  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
       entire  resulting derived work is distributed under the terms of a per-
       mission 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
       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
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