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Linux 2.6 - man page for patch (linux section 1)

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

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

       patch  tries  to  skip  any  leading  garbage,  apply the diff, and then skip any trailing
       garbage.  Thus you could feed an article or message containing a diff  listing  to  patch,
       and  it	should work.  If the entire diff is indented by a consistent amount, if lines end
       in CRLF, or if a diff is encapsulated one or more times by prepending "- " to lines start-
       ing with "-" as specified by Internet RFC 934, this is taken into account.  After removing
       indenting or encapsulation, lines beginning with # are ignored, as they are considered  to
       be comments.

       With  context  diffs,  and to a lesser extent with normal diffs, patch can detect when the
       line numbers mentioned in the patch are incorrect, and attempts to find the correct  place
       to apply each hunk of the patch.  As a first guess, it takes the line number mentioned for
       the hunk, plus or minus any offset used in applying the previous hunk.  If that is not the
       correct	place,	patch  scans  both forwards and backwards for a set of lines matching the
       context given in the hunk.  First patch looks for a place where all lines of  the  context
       match.  If no such place is found, and it's a context diff, and the maximum fuzz factor is
       set to 1 or more, then another scan takes place ignoring the first and last line  of  con-
       text.   If  that fails, and the maximum fuzz factor is set to 2 or more, the first two and
       last two lines of context are ignored, and another scan is  made.   (The  default  maximum
       fuzz factor is 2.)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

OPTIONS
       -b  or  --backup
	  Make backup files.  That is, when patching a file, rename or copy the original  instead
	  of  removing	it.   See the -V or --version-control option for details about how backup
	  file names are determined.

       --backup-if-mismatch
	  Back up a file if the patch does not match the file exactly and if backups are not oth-
	  erwise requested.  This is the default unless patch is conforming to POSIX.

       --no-backup-if-mismatch
	  Do  not  back up a file if the patch does not match the file exactly and if backups are
	  not otherwise requested.  This is the default if patch is conforming to POSIX.

       -B pref	or  --prefix=pref
	  Use the simple method to determine backup file names	(see  the  -V  method  or  --ver-
	  sion-control	method option), and append pref to a file name when generating its backup
	  file	name.	For  example,  with  -B /junk/	the   simple   backup	file   name   for
	  src/patch/util.c is /junk/src/patch/util.c.

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

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

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

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

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

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

       -E  or  --remove-empty-files
	  Remove  output files that are empty after the patches have been applied.  Normally this
	  option is unnecessary, since patch can examine the time stamps on the header to  deter-
	  mine	whether  a file should exist after patching.  However, if the input is not a con-
	  text diff or if patch is conforming to POSIX, patch does not remove empty patched files
	  unless this option is given.	When patch removes a file, it also attempts to remove any
	  empty ancestor directories.

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

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

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

       --help
	  Print a summary of options and exit.

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

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

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

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

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

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

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

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

       -o outfile  or  --output=outfile
	  Send output to outfile instead of patching files in place.  Do not use this  option  if
	  outfile  is one of the files to be patched.  When outfile is -, send output to standard
	  output, and send any messages that would usually go  to  standard  output  to  standard
	  error.

       -pnum  or  --strip=num
	  Strip  the  smallest prefix containing num leading slashes from each file name found in
	  the patch file.  A sequence of one or more adjacent slashes  is  counted  as	a  single
	  slash.   This  controls how file names found in the patch file are treated, in case you
	  keep your files in a different directory than the person who sent out the  patch.   For
	  example, supposing the file name in the patch file was

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

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

	     u/howard/src/blurfl/blurfl.c

	  without the leading slash, -p4 gives

	     blurfl/blurfl.c

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

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

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

	   o Do not remove files that are empty after patching.

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

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

	   o Do not backup files when there is a mismatch.

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

	  literal
		 Output names as-is.

	  shell  Quote names for the shell if they contain shell metacharacters  or  would  cause
		 ambiguous output.

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

	  c	 Quote names as for a C language string.

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

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

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

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

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

       --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  con-
	  text	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,  gen-
	  erate patches with UTC and use the -Z or --set-utc option instead.

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

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

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

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

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

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

	  simple  or  never
	     Make simple backups.  The -B or --prefix, -Y or --basename-prefix, and -z or  --suf-
	     fix  options  specify  the  simple  backup  file name.  If none of these options are
	     given, then  a  simple  backup  suffix  is  used;	it  is	the  value  of	the  SIM-
	     PLE_BACKUP_SUFFIX environment variable if set, and is .orig otherwise.

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

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

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

       -Y pref	or  --basename-prefix=pref
	  Use  the  simple  method  to	determine  backup file names (see the -V method or --ver-
	  sion-control method option), and prefix pref to the basename of a file name when gener-
	  ating its backup file name.  For example, with -Y .del/ the simple backup file name for
	  src/patch/util.c is src/patch/.del/util.c.

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

       -Z  or  --set-utc
	  Set the modification and access times of patched files from time stamps given  in  con-
	  text	diff  headers,	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,  Per-
	  force, or SCCS by default; see the -g or --get option.

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

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

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

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

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

FILES
       $TMPDIR/p*
	  temporary files

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

	o Traditional patch used a complicated (and incompletely documented) method to intuit the
	  name of the file to be patched from the patch header.  This method did not  conform  to
	  POSIX,  and  had  a  few gotchas.  Now patch uses a different, equally complicated (but
	  better documented) method that is optionally POSIX-conforming; we  hope  it  has  fewer
	  gotchas.   The  two methods are compatible if the file names in the context diff header
	  and the Index: line are all identical after prefix-stripping.  Your patch  is  normally
	  compatible if each header's file names all contain the same number of slashes.

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

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

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

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

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

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

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

       Computing  how to merge a hunk is significantly harder than using the standard fuzzy algo-
       rithm.  Bigger hunks, more context, a bigger offset from  the  original	location,  and	a
       worse match all slow the algorithm down.

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

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

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

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

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

					       GNU					 PATCH(1)


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