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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, 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 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
       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.
       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 --ver-
          sion-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  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.

          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
          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 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

       -N  or  --forward
          Ignore patches that seem to be reversed or already  applied.  It  is
          only checked if the first hunk of a patch can be reversed.  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.

           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:
                 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
          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.)

       --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
          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  VER-
          SION_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' 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.
          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  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).

       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.

       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
       option, and have them remove any unpatched files that depend on patched
       files (e.g. with make clean).

       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.

        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
          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.

        o 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.

        o 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 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
       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
       Grunbacher added support for merging.

                                      GNU                             PATCH(1)
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