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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 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,	if lines end in	CRLF, or if  a
       diff  is	 encapsulated  one  or	more times by prepending "- " to lines
       starting	with "-" as specified by Internet RFC 934, this	is taken  into
       account.	  After	 removing  indenting or	encapsulation, lines beginning
       with # are ignored, as they are considered to be	comments.

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

	+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, 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 de-
	  termined.

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

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

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

       --binary
	  Write	all files in binary  mode,  except  for	 standard  output  and
	  /dev/tty.  When reading, disable the heuristic for transforming CRLF
	  line endings into LF line endings.  This option is needed  on	 POSIX
	  systems when applying	patches	generated on non-POSIX systems to non-
	  POSIX	files.	(On POSIX systems, file	reads and writes never	trans-
	  form	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 ap-
	  plied.  Normally this	option is unnecessary, since patch can examine
	  the time stamps on the header	to determine whether a file should ex-
	  ist after patching.  However,	if the input is	not a context diff  or
	  if patch is conforming to POSIX, patch does not remove empty patched
	  files	unless this option is given.  When patch removes  a  file,  it
	  also attempts	to remove any empty ancestor directories.

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

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

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

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

	  The  optional	 argument  of --merge determines the output format for
	  conflicts: the diff3 format shows the	|||||||	section	with the orig-
	  inal	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  op-
	  tion into account.

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

       -N  or  --forward
	  When a patch does not	apply, patch usually checks if the patch looks
	  like it has been reversed.  The --forward option prevents that.  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.

	   +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  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 na-
	  ture being what it is.)  patch attempts to swap each hunk around be-
	  fore	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  re-
	  versed normal	diffs begin with a delete, which fails,	triggering the
	  heuristic.)

       --read-only=behavior
	  Behave as requested when trying to modify a read-only	 file:	ignore
	  the potential	problem, warn about it (the default), or fail.

       --reject-format=format
	  Produce reject files in the specified	format (either context or 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.

       --follow-symlinks
	  When looking for input files,	follow symbolic	links.	 Replaces  the
	  symbolic  links,  instead  of	modifying the files the	symbolic links
	  point	to.  Git-style patches to symbolic links will no longer	apply.
	  This	option	exists	for backwards compatibility with previous ver-
	  sions	of patch; its use is discouraged.

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

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

	  Use of this option with time stamps that do not include  time	 zones
	  is  not  recommended,	because	patches	using local time cannot	easily
	  be used by people in other time zones, and because local time	stamps
	  are  ambiguous when local clocks move	backwards during daylight-sav-
	  ing time adjustments.	 Make  sure  that  time	 stamps	 include  time
	  zones,  or generate patches with UTC and use the -Z or --set-utc op-
	  tion 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  op-
	  tion.	  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. Unless specified in the time
	  stamps, assume that the context diff headers use Coordinated Univer-
	  sal  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  de-
	  fault: 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  de-
	  fault	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 op-
	  tion.

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  di-
       rectory	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 op-
       tion, 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.

	+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-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 re-
       versed 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 en-
       tire resulting derived work is distributed under	the terms of a permis-
       sion 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
       Grunbacher added	support	for merging.

GNU								      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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