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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 pro‐
       duced by the diff program and applies those differences to one or  more
       original	 files, producing patched versions.  Normally the patched ver‐
       sions 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 usu‐
       ally 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  con‐
       taining	a  diff	 listing  to patch, and it should work.	 If the entire
       diff is indented by a consistent amount, or if a context diff  contains
       lines ending in CRLF or is encapsulated one or more times by prepending
       "- " to lines starting with "-" as specified by Internet RFC 934,  this
       is  taken  into	account.   After  removing indenting or encapsulation,
       lines beginning with # are ignored, as they are considered to  be  com‐
       ments.

       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 apply‐
       ing 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	speci‐
       fied  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 con‐
       taining 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.  When backing up a file that
	  does not exist, an empty, unreadable backup file  is	created	 as  a
	  placeholder to represent the nonexistent file.  See the -V or --ver‐
	  sion-control option for details about	 how  backup  file  names  are
	  determined.

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

       --no-backup-if-mismatch
	  Do  not  back up a file if the patch does not match the file exactly
	  and if backups are not otherwise requested.  This is the default  if
	  patch is 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.	 (On POSIX-conforming systems,
	  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 exam‐
	  ine the time stamps on the header to determine whether a file should
	  exist	 after	patching.  However, if the input is not a context diff
	  or if patch is conforming to POSIX,  patch  does  not	 remove	 empty
	  patched  files  unless  this	option is given.  When patch removes a
	  file, it also attempts to remove any empty ancestor directories.

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

       -F num  or  --fuzz=num
	  Set the maximum fuzz factor.	This option only applies to diffs that
	  have context, and causes patch to ignore up to that  many  lines  in
	  looking  for places to install a hunk.  Note that a larger fuzz fac‐
	  tor increases the odds of a faulty patch.  The default  fuzz	factor
	  is 2, and it may not be set to more than the number of lines of con‐
	  text in the context diff, ordinarily 3.

       -g num  or  --get=num
	  This option controls patch's actions when a file  is	under  RCS  or
	  SCCS	control,  and  does  not exist or is read-only and matches the
	  default version, or when a file is under ClearCase or Perforce  con‐
	  trol	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 stan‐
	  dard 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
	  Merge a patch file into the original files similar to 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
	      =======
	      lines from the patch
	      >>>>>>>

	  If there are conflicts, the user should edit the result  and	delete
	  one of the alternatives.  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 adja‐
	  cent 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  metacharac‐
		 ters 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	 vari‐
	  able 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  lit‐
	  tle 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 uni‐
	  fied).  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 VER‐
	  SION_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'	 vari‐
	  able; 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-pre‐
	     fix,  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 envi‐
	     ronment 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  environ‐
	  ment	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  directo‐
       ries.   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  syn‐
       tax:

	  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 recipi‐
       ent 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  dif‐
       ferent  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 won‐
       der whether they already applied the patch.

       Try not to have your patch modify derived files (e.g. the file  config‐
       ure  where  there  is a line configure: configure.in in your makefile),
       since the recipient should be able to regenerate the derived files any‐
       way.  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  attempt‐
       ing  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 prob‐
       lem.  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 tradi‐
       tional 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 oper‐
	  and, 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 behav‐
	  ior 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 vari‐
	  able.

	  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  bet‐
	  ter  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 identi‐
	  cal 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 ques‐
	  tion 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 con‐
       strued 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  per‐
       mission notice identical to this one.

       Permission  is granted to copy and distribute translations of this man‐
       ual into another language, under the above conditions for modified ver‐
       sions,  except  that this permission notice may be included in transla‐
       tions approved by the copyright holders instead of in the original Eng‐
       lish.

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)
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