PATCH(1)                                                              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 differ-
       ence listing produced by the diff  program  and  applies
       those differences to one or more original files, produc-
       ing 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 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, 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  consid-
       ered 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 pre-
       vious  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.)  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  ordinary  context  diff
       form regardless of the input patch's form.  If the input
       was a normal diff,  many  of  the  contexts  are  simply
       null.)  The line numbers on the hunks in the reject file
       may be different than in the patch  file:  they  reflect
       the  approximate  location patch thinks the failed hunks
       belong in the new file rather than the old one.

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

       If no original file origfile is specified on the command
       line, patch tries to figure out from the leading garbage
       what  the name of the file to edit is, using the follow-
       ing 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  mas-
          ter.

        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, something like the fol-
       lowing:

          | 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  sepa-
       rate  patch files.  This means, among other things, that
       it is assumed that the name of the file to patch must be
       determined  for  each diff listing, and that the garbage
       before each diff  listing  contains  interesting  things
       such as file names and revision level, as mentioned pre-
       viously.

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 conform-
          ing to POSIX.

       -B pref  or  --prefix=pref
          Prefix pref to a file name when generating its simple
          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
          Read  and  write all files in binary mode, except for
          standard output and /dev/tty.   This  option  has  no
          effect  on POSIX-conforming systems.  On systems like
          DOS where this option makes a difference,  the  patch
          should be generated by diff -a --binary.

       -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  unneces-
          sary,  since patch can examine the time stamps on the
          header to determine whether a file should exist after
          patching.   However,  if  the  input is not a context
          diff or if patch is conforming to POSIX,  patch  does
          not  remove empty patched files unless this option is
          given.  When patch removes a file, it  also  attempts
          to remove any empty ancestor directories.

       -f  or  --force
          Assume  that the user knows exactly what he or she is
          doing, and do not ask any  questions.   Skip  patches
          whose headers do not say which file is to be patched;
          patch files even though they have the  wrong  version
          for  the  Prereq:  line in the patch; and assume that
          patches are not reversed even if they look like  they
          are.   This  option does not suppress commentary; use
          -s for that.

       -F num  or  --fuzz=num
          Set  the  maximum  fuzz  factor.   This  option  only
          applies  to diffs that have context, and causes patch
          to ignore up to that many lines 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, and it may not be set to more than
          the number of lines of context 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 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 if patch is conforming
          to POSIX, negative otherwise.

       --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.

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

       -N  or  --forward
          Ignore patches that seem to be  reversed  or  already
          applied.  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.

       -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  fol-
          lows.

           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 --quot-
          ing-style option with the environment variable  QUOT-
          ING_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.

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

          If the first hunk of a patch  fails,  patch  reverses
          the hunk to see if it can be applied that way.  If it
          can, you are asked if you want to have the -R  option
          set.   If it can't, the patch continues to be applied
          normally.   (Note:  this  method  cannot   detect   a
          reversed  patch  if  it  is  a normal diff and if the
          first command is an append (i.e. it should have  been
          a  delete)  since  appends always succeed, due to the
          fact that a null context matches anywhere.   Luckily,
          most  patches  add or change lines rather than delete
          them, so most reversed  normal  diffs  begin  with  a
          delete, which fails, triggering the heuristic.)

       -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  con-
          tain  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.

       -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) environ-
          ment  variable,  which  is overridden by this option.
          The method does not affect whether backup  files  are
          made;  it  affects only the names of any backup files
          that are made.

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

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

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

          simple  or  never
             Make  simple  backups.   The -B or --prefix, -Y or
             --basename-prefix,  and  -z  or  --suffix  options
             specify  the  simple backup file name.  If none of
             these options are given, then a simple backup suf-
             fix   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
          Prefix pref to the basename of a file name when  gen-
          erating  its  simple  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 suffix as the simple backup suffix.  For example,
          with  -z -  the   simple   backup   file   name   for
          src/patch/util.c  is  src/patch/util.c-.   The backup
          suffix  may   also   be   specified   by   the   SIM-
          PLE_BACKUP_SUFFIX   environment  variable,  which  is
          overridden by this option.

       -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  Coordi-
          nated 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 nor-
          mally  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  con-
          tents  have  not  changed.   Also,  if  you use these
          options, you should remove (e.g. with make clean) all
          files that depend on the patched files, so that later
          invocations of  make  do  not  get  confused  by  the
          patched files' times.

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

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

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

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

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

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

FILES
       $TMPDIR/p*
          temporary files

       /dev/tty
          controlling  terminal;  used  to get answers to ques-
          tions asked of the user

SEE ALSO
       diff(1), ed(1)

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

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

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

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

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

       You can save people a lot of grief by keeping  a  patch-
       level.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  warn-
       ing.

       You  can  create  a file by sending out a diff that com-
       pares  /dev/null  or  an  empty  file  dated  the  Epoch
       (1970-01-01  00:00:00  UTC) to the file you want to cre-
       ate.  This only works if the file  you  want  to  create
       doesn't  exist  already  in  the target directory.  Con-
       versely, 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: con-
       figure.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 hay-
       wire.

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 suc-
       cessfully, 1 if some hunks cannot be applied, 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  accom-
       pany 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.  Until  a
       suitable  interactive  interface  is  added,  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 equivalent to  -p0.   The
          -p  option  now  requires an operand, and -p 0 is now
          equivalent to -p0.  For  maximum  compatibility,  use
          options like -p0 and -p1.

          Also,  traditional  patch simply counted slashes when
          stripping path prefixes; patch  now  counts  pathname
          components.  That is, a sequence of one or more adja-
          cent slashes now counts as a single slash.  For maxi-
          mum  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  conforming to POSIX with the --posix
          option or by setting the POSIXLY_CORRECT  environment
          variable.

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

        o Traditional patch  used  a  complicated  (and  incom-
          pletely  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 compli-
          cated  (but better documented) method that is option-
          ally 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 nor-
          mally compatible if each header's file names all con-
          tain 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 ques-
          tions  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 con-
          forms to POSIX.  Spaces are significant in  the  fol-
          lowing 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>.

       patch  could  be  smarter  about partial matches, exces-
       sively deviant offsets and swapped code, but that  would
       take an extra pass.

       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  suc-
       ceeded 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.

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  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  verba-
       tim  copying, provided that the entire resulting derived
       work is distributed under  the  terms  of  a  permission
       notice identical to this one.

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

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



GNU                               2002/05/25                          PATCH(1)