Provided by: patch_2.7.1-4_amd64 bug

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
       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 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
       suspicious.  If the --verbose option is given, you are also told about  hunks  that  match
       exactly.

       If  no  original file origfile is specified on the command line, patch tries to figure out
       from the leading garbage what the name of the file to edit is, using the following rules.

       First, patch takes an ordered list of candidate file names as follows:

        · If the header is that of a context diff, patch takes the old and new file names in  the
          header.   A  name is ignored if it does not have enough slashes to satisfy the -pnum or
          --strip=num option.  The name /dev/null is also ignored.

        · If there is an Index: line in the leading garbage and if either the old and  new  names
          are  both absent or if patch is conforming to POSIX, patch takes the name in the Index:
          line.

        · For the purpose of the following rules, the candidate file names are considered  to  be
          in the order (old, new, index), regardless of the order that they appear in the header.

       Then patch selects a file name from the candidate list as follows:

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

        · If patch is not ignoring  RCS,  ClearCase,  Perforce,  and  SCCS  (see  the  -g num  or
          --get=num  option),  and  no named files exist but an RCS, ClearCase, Perforce, or SCCS
          master is found, patch selects the first named file with an RCS,  ClearCase,  Perforce,
          or SCCS master.

        · If  no  named  files exist, no RCS, ClearCase, Perforce, or SCCS master was found, some
          names are given, patch is not conforming to POSIX, and the patch appears  to  create  a
          file, patch selects the best name requiring the creation of the fewest directories.

        · If  no  file  name results from the above heuristics, you are asked for the name of the
          file to patch, and patch selects that name.

       To determine the best of a nonempty list of file names, patch first takes  all  the  names
       with  the  fewest  path  name  components;  of those, it then takes all the names with the
       shortest basename; of those, it then takes all the shortest names; finally, it  takes  the
       first remaining name.

       Additionally,  if  the leading garbage contains a Prereq: line, patch takes the first word
       from the prerequisites line (normally a version number) and checks the  original  file  to
       see if that word can be found.  If not, patch asks for confirmation before proceeding.

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

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

       and patch a file in the blurfl directory directly from the article 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
       revision level, as mentioned previously.

OPTIONS

       -b  or  --backup
          Make backup files.  That is, when patching a file, rename or copy the original  instead
          of  removing  it.   See the -V or --version-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  transform  line
          endings. On Windows, reads and writes do transform line endings by default, and patches
          should be generated by diff --binary when line endings are significant.)

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

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

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

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

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

       -E  or  --remove-empty-files
          Remove  output files that are empty after the patches have been applied.  Normally this
          option is unnecessary, 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 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
          conflict  is  found, patch outputs a warning and brackets the conflict with <<<<<<< and
          >>>>>>> lines.  A typical conflict will look like this:

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

          The optional argument of --merge determines the output format for conflicts: the  diff3
          format  shows  the ||||||| section with the 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.

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

           · Do not remove files that are empty after patching.

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

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

           · Do not backup files when there is a mismatch.

       --quoting-style=word
          Use style word to quote output names.  The word should be one of the following:

          literal
                 Output names as-is.

          shell  Quote  names  for  the shell if they contain shell 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
          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 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
          symbolic  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
          context diff headers.  Unless specified in the time stamps,  assume  that  the  context
          diff headers use local time.

          Use  of this option with time stamps that do not include time zones is not recommended,
          because patches using local time cannot easily be used by people in other  time  zones,
          and  because  local  time  stamps are ambiguous when local clocks move backwards during
          daylight-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
          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  suffix  is  used;  it   is   the   value   of   the
             SIMPLE_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
          --version-control method option), and prefix pref to the basename of a file  name  when
          generating  its  backup  file  name.  For example, with -Y .del/ the simple backup file
          name for src/patch/util.c is src/patch/.del/util.c.

       -z suffix  or  --suffix=suffix
          Use  the  simple  method  to  determine  backup  file  names  (see  the  -V  method  or
          --version-control method option), and use suffix as the suffix.  For example, with -z -
          the backup file name for src/patch/util.c is src/patch/util.c-.

       -Z  or  --set-utc
          Set the modification and access times of  patched  files  from  time  stamps  given  in
          context diff headers. Unless specified in the time stamps, assume that the context diff
          headers use Coordinated 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,
          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 --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
       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 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.

        · 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 adjacent slashes now
          counts as a single slash.  For maximum portability, avoid sending patches containing //
          in file names.

        · In  traditional  patch,  backups were enabled by default.  This 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 equivalent to the -b -z suffix options of
          GNU patch.

        · Traditional patch used a complicated (and incompletely documented) method to intuit the
          name  of  the file to be patched from the patch header.  This method did not conform to
          POSIX, and had a few gotchas.  Now patch uses a  different,  equally  complicated  (but
          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.

        · 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.

        · Traditional  patch  exited with a status value that counted the number of bad hunks, or
          with status 1 if there was real trouble.  Now patch exits with status 1 if  some  hunks
          failed, or with 2 if there was real trouble.

        · Limit  yourself to the following options when sending instructions meant to be executed
          by anyone running GNU patch, traditional patch, or a  patch  that  conforms  to  POSIX.
          Spaces are significant in the following list, and operands are required.

             -c
             -d dir
             -D define
             -e
             -l
             -n
             -N
             -o outfile
             -pnum
             -R
             -r rejectfile

BUGS

       Please report bugs via email to <bug-patch@gnu.org>.

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

       If  you  apply  a  patch  you've already applied, patch thinks it is a 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
       algorithm.   Bigger hunks, more context, a bigger offset from the original location, and a
       worse match all slow the algorithm down.

COPYING

       Copyright (C) 1984, 1985, 1986, 1988 Larry Wall.
       Copyright (C) 1989, 1990, 1991, 1992, 1993, 1994, 1995,  1996,  1997,  1998,  1999,  2000,
       2001, 2002, 2009 Free Software Foundation, Inc.

       Permission  is  granted to make and distribute verbatim copies of this manual provided the
       copyright notice and this permission notice are preserved on all copies.

       Permission is granted to copy and distribute modified versions of this  manual  under  the
       conditions  for  verbatim  copying,  provided  that  the  entire resulting derived work is
       distributed under the terms of a permission notice identical to this one.

       Permission is granted to copy and distribute translations  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 contributors include Wayne Davison, who added unidiff
       support, and David  MacKenzie,  who  added  configuration  and  backup  support.   Andreas
       Grünbacher added support for merging.