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PATCH(1)		    General Commands Manual		      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 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.

       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.)  If
       patch cannot find a place to install that hunk of the  patch,  it  puts
       the hunk	out to a reject	file, which normally is	the name of the	output
       file plus a .rej	suffix,	or # if	.rej would generate a file  name  that
       is  too	long  (if even appending the single character #	makes the file
       name too	long, then # replaces the file name's last  character).	  (The
       rejected	hunk comes out in ordinary context diff	form regardless	of the
       input patch's form.  If the input was a normal diff, many of  the  con-
       texts  are  simply  null.)  The line numbers on the hunks in the	reject
       file may	be different than in the patch file: they reflect the approxi-
       mate  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:

	+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, and SCCS (see the -g	num or
	  --get=num option), and no named files	exist but an  RCS,  ClearCase,
	  or  SCCS master is found, patch selects the first named file with an
	  RCS, ClearCase, or SCCS master.

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

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

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

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

       The  upshot  of	all this is that you should be able to say, while in a
       news interface, something like the 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
	  Prefix  pref	to  a file name	when generating	its simple backup file
	  name.	 For example, with -B /junk/ the simple	backup file  name  for
	  src/patch/util.c is /junk/src/patch/util.c.

       --binary
	  Read	and write all files in binary mode, except for standard	output
	  and /dev/tty.	 This option has no effect  on	POSIX-conforming  sys-
	  tems.	 On systems like DOS where this	option makes a difference, the
	  patch	should be generated by diff -a --binary.

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

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

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

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

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

       -E  or  --remove-empty-files
	  Remove output	files that are	empty  after  the  patches  have  been
	  applied.  Normally this option is 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 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,  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 vari-
	  able if it is	set; if	not, the default value is  zero	 if  patch  is
	  conforming to	POSIX, negative	otherwise.

       --help
	  Print	a summary of options and exit.

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

       -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.

       -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.

	   +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, 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 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.

       -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.)

       -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
	  Prefix pref to the basename of a file	name when generating its  sim-
	  ple  backup file name.  For example, with -Y .del/ the simple	backup
	  file name for	src/patch/util.c is src/patch/.del/util.c.

       -z suffix  or  --suffix=suffix
	  Use suffix as	the simple backup suffix.  For example,	with -z	-  the
	  simple  backup  file name for	src/patch/util.c is src/patch/util.c-.
	  The backup suffix may	also be	specified by the  SIMPLE_BACKUP_SUFFIX
	  environment variable,	which is overridden by this option.

       -Z  or  --set-utc
	  Set  the  modification  and  access times of patched files from time
	  stamps given in context diff headers,	assuming that the context diff
	  headers  use	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, 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)

       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, 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.  Until a suitable interactive interface is added, you should prob-
       ably 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.

	+o In  traditional  patch,  the -p option's operand was optional, and a
	  bare -p was equivalent to -p0.  The -p option	now requires an	 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.

	+o 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.

	+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 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.

	+o 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.

	+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-gnu-utils@gnu.org>.

       patch could be smarter about partial matches, excessively deviant  off-
       sets and	swapped	code, but that would take an extra pass.

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

COPYING
       Copyright 1984, 1985, 1986, 1988	Larry Wall.
       Copyright 1989, 1990, 1991, 1992, 1993, 1994, 1995,  1996,  1997,  1998
       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.

GNU				  1998/03/21			      PATCH(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | FILES | SEE ALSO | NOTES FOR PATCH SENDERS | DIAGNOSTICS | CAVEATS | COMPATIBILITY ISSUES | BUGS | COPYING | AUTHORS

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