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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 produced by the diff
       program and applies those differences to one or more  original  files,  producing  patched
       versions.   Normally  the patched versions are put in place of the originals.  Backups can
       be made; see the -b or --backup option.  The names of the files to be patched are  usually
       taken  from the patch file, but if there's just one file to be patched it can be specified
       on the command line as originalfile.

       Upon startup, patch attempts to determine the type of the diff listing,  unless  overruled
       by  a  -c  (--context), -e (--ed), -n (--normal), or -u (--unified) option.  Context diffs
       (old-style, new-style, and unified) and normal diffs are  applied  by  the  patch  program
       itself, while ed diffs are simply fed to the ed(1) editor via a pipe.

       patch  tries  to  skip  any  leading  garbage,  apply the diff, and then skip any trailing
       garbage.  Thus you could feed an article or message containing a diff  listing  to  patch,
       and  it  should work.  If the entire diff is indented by a consistent amount, if lines end
       in CRLF, or if a diff is encapsulated one or more times by prepending "- " to lines start-
       ing 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  con-
       text.   If  that fails, and the maximum fuzz factor is set to 2 or more, the first two and
       last two lines of context are ignored, and another scan is  made.   (The  default  maximum
       fuzz factor is 2.)

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

       If  patch cannot find a place to install that hunk of the patch, it puts the hunk out to a
       reject file, which normally is the name of the output file plus a .rej  suffix,  or  #  if
       .rej would generate a file name that is too long (if even appending the single character #
       makes the file name too long, then # replaces the file name's last character).

       The rejected hunk comes out in unified or context diff format.  If the input was a  normal
       diff,  many  of the contexts are simply null.  The line numbers on the hunks in the reject
       file may be different than in the patch file: they reflect the approximate location  patch
       thinks the failed hunks belong in the new file rather than the old one.

       As  each  hunk is completed, you are told if the hunk failed, and if so which line (in the
       new file) patch thought the hunk should go on.  If the hunk is installed  at  a  different
       line  from the line number specified in the diff, you are told the offset.  A single large
       offset may indicate that a hunk was installed in the wrong place.  You are also told if  a
       fuzz  factor  was used to make the match, in which case you should also be slightly suspi-
       cious.  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.

       The upshot of all this is that you should be able to say, while in a news interface, some-
       thing like the following:

          | patch -d /usr/src/local/blurfl

       and patch a file in the blurfl directory directly from the article containing the patch.

       If the patch file contains more than one patch, patch tries to apply each of  them  as  if
       they  came  from separate patch files.  This means, among other things, that it is assumed
       that the name of the file to patch must be determined for each diff listing, and that  the
       garbage  before each diff listing contains interesting things such as file names and revi-
       sion level, as mentioned previously.

OPTIONS
       -b  or  --backup
          Make backup files.  That is, when patching a file, rename or copy the original  instead
          of  removing  it.   When  backing  up  a file that does not exist, an empty, unreadable
          backup file is created as a placeholder to represent the nonexistent file.  See the  -V
          or --version-control option for details about how backup file names are determined.

       --backup-if-mismatch
          Back up a file if the patch does not match the file exactly and if backups are not oth-
          erwise 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 --ver-
          sion-control method option), and append pref to a file name when generating its  backup
          file   name.    For   example,   with   -B /junk/  the  simple  backup  file  name  for
          src/patch/util.c is /junk/src/patch/util.c.

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

       -c  or  --context
          Interpret the patch file as a ordinary context diff.

       -d dir  or  --directory=dir
          Change to the directory dir immediately, before doing anything else.

       -D define  or  --ifdef=define
          Use the #ifdef ... #endif construct to mark changes, with define as the differentiating
          symbol.

       --dry-run
          Print the results of applying the patches without actually changing any files.

       -e  or  --ed
          Interpret the patch file as an ed script.

       -E  or  --remove-empty-files
          Remove output files that are empty after the patches have been applied.  Normally  this
          option  is unnecessary, since patch can examine the time stamps on the header to deter-
          mine whether a file should exist after patching.  However, if the input is not  a  con-
          text 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 ques-
          tions.  Skip patches whose headers do not say which file is to be patched; patch  files
          even  though  they have the wrong version for the Prereq: line in the patch; and assume
          that patches are not reversed even if they look like they are.  This  option  does  not
          suppress commentary; use -s for that.

       -F num  or  --fuzz=num
          Set  the maximum fuzz factor.  This option only applies to diffs that have context, and
          causes patch to ignore up to that many lines  of  context  in  looking  for  places  to
          install  a  hunk.  Note that a larger fuzz factor increases the odds of a faulty patch.
          The default fuzz factor is 2.  A fuzz factor greater than or equal  to  the  number  of
          lines of context in the context diff, ordinarily 3, ignores all context.

       -g num  or  --get=num
          This option controls patch's actions when a file is under RCS or SCCS control, and does
          not exist or is read-only and matches the default version, or  when  a  file  is  under
          ClearCase  or  Perforce control and does not exist.  If num is positive, patch gets (or
          checks out) the file from the revision control system;  if  zero,  patch  ignores  RCS,
          ClearCase,  Perforce,  and  SCCS and does not get the file; and if negative, patch asks
          the user whether to get the file.  The default value of this option  is  given  by  the
          value  of the PATCH_GET environment variable if it is set; if not, the default value is
          zero.

       --help
          Print a summary of options and exit.

       -i patchfile  or  --input=patchfile
          Read the patch from patchfile.  If patchfile  is  -,  read  from  standard  input,  the
          default.

       -l  or  --ignore-whitespace
          Match  patterns  loosely,  in  case tabs or spaces have been munged in your files.  Any
          sequence of one or more blanks in the patch file matches any sequence in  the  original
          file, and sequences of blanks at the ends of lines are ignored.  Normal characters must
          still match exactly.  Each line of the context must still match a line in the  original
          file.

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

              <<<<<<<
              lines from the original file
              |||||||
              original lines from the patch
              =======
              new lines from the patch
              >>>>>>>

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

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

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

       -N  or  --forward
          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 adjacent slashes  is  counted  as  a  single
          slash.   This  controls how file names found in the patch file are treated, in case you
          keep your files in a different directory than the person who sent out the  patch.   For
          example, supposing the file name in the patch file was

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

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

             u/howard/src/blurfl/blurfl.c

          without the leading slash, -p4 gives

             blurfl/blurfl.c

          and  not  specifying  -p  at  all just gives you blurfl.c.  Whatever you end up with is
          looked for either in the current directory,  or  the  directory  specified  by  the  -d
          option.

       --posix
          Conform more strictly to the POSIX standard, as follows.

           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 metacharacters  or  would  cause
                 ambiguous output.

          shell-always
                 Quote names for the shell, even if they would normally not require quoting.

          c      Quote names as for a C language string.

          escape Quote as with c except omit the surrounding double-quote characters.

          You  can  specify  the default value of the --quoting-style option with the environment
          variable QUOTING_STYLE.  If that environment variable is not set, the default value  is
          shell.

       -r rejectfile  or  --reject-file=rejectfile
          Put  rejects  into  rejectfile instead of the default .rej file.  When rejectfile is -,
          discard rejects.

       -R  or  --reverse
          Assume that this patch was created with the old  and  new  files  swapped.   (Yes,  I'm
          afraid  that  does happen occasionally, human nature being what it is.)  patch attempts
          to swap each hunk around before applying it.  Rejects come out in the  swapped  format.
          The  -R  option does not work with ed diff scripts because there is too little informa-
          tion 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 prob-
          lem, warn about it (the default), or fail.

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

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

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

       -t  or  --batch
          Suppress  questions  like  -f,  but make some different assumptions: skip patches whose
          headers do not contain file names (the same as -f); skip patches for which the file has
          the  wrong  version  for  the  Prereq:  line  in the patch; and assume that patches are
          reversed if they look like they are.

       -T  or  --set-time
          Set the modification and access times of patched files from time stamps given  in  con-
          text  diff  headers.  Unless specified in the time stamps, assume that the context diff
          headers use local time.

          Use of this option with time stamps that do not include time zones is not  recommended,
          because  patches  using local time cannot easily be used by people in other time zones,
          and because local time stamps are ambiguous when local  clocks  move  backwards  during
          daylight-saving  time  adjustments.   Make sure that time stamps include time zones, or
          generate patches with UTC and use the -Z or --set-utc option instead.

       -u  or  --unified
          Interpret the patch file as a unified context diff.

       -v  or  --version
          Print out patch's revision header and patch level, and exit.

       -V method  or  --version-control=method
          Use method to determine backup file names.   The  method  can  also  be  given  by  the
          PATCH_VERSION_CONTROL  (or,  if  that's not set, the VERSION_CONTROL) environment vari-
          able, which is overridden by this option.  The method does not  affect  whether  backup
          files are made; it affects only the names of any backup files that are made.

          The value of method is like the GNU Emacs `version-control' variable; patch also recog-
          nizes synonyms that are more descriptive.  The valid  values  for  method  are  (unique
          abbreviations are accepted):

          existing  or  nil
             Make  numbered  backups  of  files that already have them, otherwise simple backups.
             This is the default.

          numbered  or  t
             Make numbered backups.  The numbered backup file name for F is F.~N~ where N is  the
             version number.

          simple  or  never
             Make  simple backups.  The -B or --prefix, -Y or --basename-prefix, and -z or --suf-
             fix 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 SIM-
             PLE_BACKUP_SUFFIX environment variable if set, and is .orig otherwise.

          With numbered or simple backups, if the backup file name is too long, the backup suffix
          ~  is  used  instead; if even appending ~ would make the name too long, then ~ replaces
          the last character of the file name.

       --verbose
          Output extra information about the work being done.

       -x num  or  --debug=num
          Set internal debugging flags of interest only to patch patchers.

       -Y pref  or  --basename-prefix=pref
          Use the simple method to determine backup file names  (see  the  -V  method  or  --ver-
          sion-control method option), and prefix pref to the basename of a file name when gener-
          ating 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 --ver-
          sion-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 con-
          text diff headers. Unless specified in the time stamps, assume that  the  context  diff
          headers  use  Coordinated Universal Time (UTC, often known as GMT).  Also see the -T or
          --set-time option.

          The -Z or --set-utc and -T or --set-time options normally refrain from setting a file's
          time  if the file's original time does not match the time given in the patch header, or
          if its contents do not match the patch exactly.  However, if the -f or  --force  option
          is given, the file time is set regardless.

          Due  to the limitations of diff output format, these options cannot update the times of
          files whose contents have not changed.  Also, if you  use  these  options,  you  should
          remove (e.g. with make clean) all files that depend on the patched files, so that later
          invocations of make do not get confused by the patched files' times.

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

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

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

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

       TMPDIR, TMP, TEMP
          Directory to put temporary files in; patch uses the first environment variable in  this
          list  that  is  set.   If none are set, the default is system-dependent; it is normally
          /tmp on Unix hosts.

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

FILES
       $TMPDIR/p*
          temporary files

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

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

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

NOTES FOR PATCH SENDERS
       There  are  several  things  you  should  bear  in mind if you are going to be sending out
       patches.

       Create your patch systematically.  A good method is the command  diff -Naur old new  where
       old  and  new identify the old and new directories.  The names old and new should not con-
       tain any slashes.  The diff command's headers should have dates  and  times  in  Universal
       Time  using  traditional Unix format, so that patch recipients can use the -Z or --set-utc
       option.  Here is an example command, using Bourne shell syntax:

          LC_ALL=C TZ=UTC0 diff -Naur gcc-2.7 gcc-2.8

       Tell your recipients how to apply the patch by telling them which directory to cd to,  and
       which  patch  options to use.  The option string -Np1 is recommended.  Test your procedure
       by pretending to be a recipient and applying your patch to a copy of the original files.

       You can save people a lot of grief by keeping a patchlevel.h  file  which  is  patched  to
       increment  the patch level as the first diff in the patch file you send out.  If you put a
       Prereq: line in with the patch, it won't let them apply patches out of order without  some
       warning.

       You can create a file by sending out a diff that compares /dev/null or an empty file dated
       the Epoch (1970-01-01 00:00:00 UTC) to the file you want to create.  This  only  works  if
       the  file  you  want to create doesn't exist already in the target directory.  Conversely,
       you can remove a file by sending out a context diff that compares the file to  be  deleted
       with  an  empty file dated the Epoch.  The file will be removed unless patch is conforming
       to POSIX and the -E or --remove-empty-files option is not given.  An easy way to  generate
       patches that create and remove files is to use GNU diff's -N or --new-file option.

       If  the  recipient  is  supposed to use the -pN option, do not send output that looks like
       this:

          diff -Naur v2.0.29/prog/README prog/README
          --- v2.0.29/prog/README   Mon Mar 10 15:13:12 1997
          +++ prog/README   Mon Mar 17 14:58:22 1997

       because the two file names have different numbers of slashes, and  different  versions  of
       patch  interpret  the  file names differently.  To avoid confusion, send output that looks
       like this instead:

          diff -Naur v2.0.29/prog/README v2.0.30/prog/README
          --- v2.0.29/prog/README   Mon Mar 10 15:13:12 1997
          +++ v2.0.30/prog/README   Mon Mar 17 14:58:22 1997


       Avoid sending patches that compare backup file names like README.orig,  since  this  might
       confuse patch into patching a backup file instead of the real file.  Instead, send patches
       that compare the same base file  names  in  different  directories,  e.g.  old/README  and
       new/README.

       Take  care  not  to  send  out reversed patches, since it makes people wonder whether they
       already applied the patch.

       Try not to have your patch modify derived files (e.g. the file configure where there is  a
       line  configure:  configure.in  in  your  makefile), since the recipient should be able to
       regenerate the derived files anyway.  If you must send diffs of  derived  files,  generate
       the  diffs using UTC, have the recipients apply the patch with the -Z or --set-utc option,
       and have them remove  any  unpatched  files  that  depend  on  patched  files  (e.g.  with
       make clean).

       While  you may be able to get away with putting 582 diff listings into one file, it may be
       wiser to group related patches into separate files in case something goes haywire.

DIAGNOSTICS
       Diagnostics generally indicate that patch couldn't parse your patch file.

       If the --verbose option is given, the message Hmm... indicates that there  is  unprocessed
       text  in the patch file and that patch is attempting to intuit whether there is a patch in
       that text and, if so, what kind of patch it is.

       patch's exit status is 0 if all hunks are applied successfully, 1 if some hunks cannot  be
       applied  or  there  were  merge  conflicts,  and 2 if there is more serious trouble.  When
       applying a set of patches in a loop it behooves you to check this exit status so you don't
       apply a later patch to a partially patched file.

CAVEATS
       Context  diffs  cannot  reliably  represent the creation or deletion of empty files, empty
       directories, or special files such as symbolic links.  Nor can they represent  changes  to
       file  metadata like ownership, permissions, or whether one file is a hard link to another.
       If changes like these are also required, separate instructions (e.g. a  shell  script)  to
       accomplish them should accompany the patch.

       patch  cannot  tell  if  the line numbers are off in an ed script, and can detect bad line
       numbers in a normal diff only when it finds a change or deletion.  A  context  diff  using
       fuzz  factor  3 may have the same problem.  You should probably do a context diff in these
       cases to see if the changes made sense.  Of course, compiling without errors is  a  pretty
       good indication that the patch worked, but not always.

       patch  usually  produces  the  correct  results, even when it has to do a lot of guessing.
       However, the results are guaranteed to be correct  only  when  the  patch  is  applied  to
       exactly the same version of the file that the patch was generated from.

COMPATIBILITY ISSUES
       The POSIX standard specifies behavior that differs from patch's traditional behavior.  You
       should be aware of these differences if you must interoperate with patch versions 2.1  and
       earlier, which do not conform to POSIX.

        o In  traditional  patch, the -p option's operand was optional, and a bare -p was equiva-
          lent to -p0.  The -p option now requires an operand, and -p 0 is now equivalent to -p0.
          For maximum compatibility, use options like -p0 and -p1.

          Also,  traditional patch simply counted slashes when stripping path prefixes; patch now
          counts pathname components.  That is, a sequence of one or more  adjacent  slashes  now
          counts as a single slash.  For maximum portability, avoid sending patches containing //
          in file names.

        o In traditional patch, backups were enabled by default.  This behavior  is  now  enabled
          with the -b or --backup option.

          Conversely,  in POSIX patch, backups are never made, even when there is a mismatch.  In
          GNU patch, this behavior is enabled with the --no-backup-if-mismatch option, or by con-
          forming  to POSIX with the --posix option or by setting the POSIXLY_CORRECT environment
          variable.

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

        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
          better documented) method that is optionally POSIX-conforming; we  hope  it  has  fewer
          gotchas.   The  two methods are compatible if the file names in the context diff header
          and the Index: line are all identical after prefix-stripping.  Your patch  is  normally
          compatible if each header's file names all contain the same number of slashes.

        o When  traditional  patch  asked  the  user a question, it sent the question to standard
          error and looked for an answer from the first file in the following  list  that  was  a
          terminal:  standard  error,  standard  output, /dev/tty, and standard input.  Now patch
          sends questions to standard output and gets answers from /dev/tty.  Defaults  for  some
          answers  have  been  changed  so that patch never goes into an infinite loop when using
          default answers.

        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 AT gnu.org>.

       If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... #endif), patch
       is  incapable  of  patching  both versions, and, if it works at all, will likely patch the
       wrong one, and tell you that it succeeded to boot.

       If you apply a patch you've already applied, patch thinks it  is  a  reversed  patch,  and
       offers to un-apply the patch.  This could be construed as a feature.

       Computing  how to merge a hunk is significantly harder than using the standard fuzzy algo-
       rithm.  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  dis-
       tributed under the terms of a permission notice identical to this one.

       Permission is granted to copy and distribute translations of this manual into another lan-
       guage, under the above conditions for  modified  versions,  except  that  this  permission
       notice may be included in translations approved by the copyright holders instead of in the
       original English.

AUTHORS
       Larry Wall wrote the original version of patch.  Paul  Eggert  removed  patch's  arbitrary
       limits;  added  support for binary files, setting file times, and deleting files; and made
       it conform better to POSIX.  Other contributors include Wayne Davison, who  added  unidiff
       support,  and  David  MacKenzie,  who  added  configuration  and  backup support.  Andreas
       Grunbacher added support for merging.



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