Provided by: patch_2.6.1-3_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.  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.)

       --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.

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

       -T  or  --set-time
          Set the modification and access times of  patched  files  from  time  stamps  given  in
          context  diff  headers,  assuming  that  the context diff headers use local time.  This
          option is not recommended, because patches using local time cannot easily  be  used  by
          people  in  other  time  zones,  and because local time stamps are ambiguous when local
          clocks move backwards during daylight-saving time adjustments.  Instead of  using  this
          option, generate patches with UTC and use the -Z or --set-utc option instead.

       -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, assuming that the context diff headers use Coordinated Universal
          Time (UTC, often known as GMT).  Also see the -T or --set-time option.

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

                                               GNU                                       PATCH(1)