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

PATCH(P)			    POSIX Programmer's Manual				 PATCH(P)

NAME
       patch - apply changes to files

SYNOPSIS
       patch [-blNR][ -c| -e| -n][-d dir][-D define][-i patchfile]
	       [-o outfile][-p num][-r rejectfile][file]

DESCRIPTION
       The  patch  utility  shall read a source (patch) file containing any of the three forms of
       difference (diff) listings produced by the diff utility (normal, context, or in the  style
       of  ed) and apply those differences to a file. By default, patch shall read from the stan-
       dard input.

       The patch utility shall attempt to determine the type of the diff  listing,  unless  over-
       ruled by a -c, -e, or -n option.

       If  the patch file contains more than one patch, patch shall attempt to apply each of them
       as if they came from separate patch files. (In this case,  the  application  shall  ensure
       that the name of the patch file is determinable for each diff listing.)

OPTIONS
       The  patch  utility  shall conform to the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -b     Save a copy of the original contents of each modified file, before the  differences
	      are  applied,  in  a file of the same name with the suffix .orig appended to it. If
	      the file already exists, it shall be overwritten; if multiple patches  are  applied
	      to  the  same  file, the .orig file shall be written only for the first patch. When
	      the -o outfile option is also specified, file .orig shall not be	created  but,  if
	      outfile already exists, outfile .orig shall be created.

       -c     Interpret  the  patch  file as a context difference (the output of the utility diff
	      when the -c or -C options are specified).

       -d  dir
	      Change the current directory to dir before processing as described in the  EXTENDED
	      DESCRIPTION section.

       -D  define
	      Mark changes with one of the following C preprocessor constructs:

	      #ifdef define
	      ...
	      #endif

	      #ifndef define
	      ...
	      #endif

       optionally  combined with the C preprocessor construct #else.  If the patched file is pro-
       cessed with the C preprocessor, where the macro define is defined, the output  shall  con-
       tain  the changes from the patch file; otherwise, the output shall not contain the patches
       specified in the patch file.

       -e     Interpret the patch file as an ed script, rather than a diff script.

       -i  patchfile
	      Read the patch information from the file named by the  pathname  patchfile,  rather
	      than the standard input.

       -l     (The  letter ell.) Cause any sequence of <blank>s in the difference script to match
	      any sequence of <blank>s in the input  file.  Other  characters  shall  be  matched
	      exactly.

       -n     Interpret the script as a normal difference.

       -N     Ignore  patches  where  the  differences	have already been applied to the file; by
	      default, already-applied patches shall be rejected.

       -o  outfile
	      Instead of modifying the files (specified by the file  operand  or  the  difference
	      listings)  directly,  write  a  copy of the file referenced by each patch, with the
	      appropriate differences applied, to outfile. Multiple patches  for  a  single  file
	      shall  be  applied to the intermediate versions of the file created by any previous
	      patches, and shall result in multiple, concatenated  versions  of  the  file  being
	      written to outfile.

       -p  num
	      For all pathnames in the patch file that indicate the names of files to be patched,
	      delete num pathname components from the beginning of each pathname. If the pathname
	      in  the  patch  file is absolute, any leading slashes shall be considered the first
	      component (that is, -p 1 shall remove the leading slashes).  Specifying -p 0  shall
	      cause  the full pathname to be used. If -p is not specified, only the basename (the
	      final pathname component) shall be used.

       -R     Reverse the sense of the patch script; that is, assume that the  difference  script
	      was  created  from the new version to the old version. The -R option cannot be used
	      with ed scripts.	The patch utility shall attempt to reverse each  portion  of  the
	      script  before  applying it. Rejected differences shall be saved in swapped format.
	      If this option is not specified, and until a portion of the patch file is  success-
	      fully  applied,  patch attempts to apply each portion in its reversed sense as well
	      as in its normal sense. If the attempt is successful, the user shall be prompted to
	      determine whether the -R option should be set.

       -r  rejectfile
	      Override	the  default  reject filename. In the default case, the reject file shall
	      have the same name as the output file, with the suffix .rej  appended  to  it;  see
	      Patch Application .

OPERANDS
       The following operand shall be supported:

       file   A pathname of a file to patch.

STDIN
       See the INPUT FILES section.

INPUT FILES
       Input files shall be text files.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of patch:

       LANG   Provide  a  default  value for the internationalization variables that are unset or
	      null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Inter-
	      nationalization Variables for the precedence of internationalization variables used
	      to determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the  other  interna-
	      tionalization variables.

       LC_CTYPE
	      Determine  the  locale for the interpretation of sequences of bytes of text data as
	      characters (for example, single-byte as opposed to multi-byte characters	in  argu-
	      ments and input files).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error and informative messages written to stan-
	      dard output.

       NLSPATH
	      Determine the location of message catalogs for the processing of LC_MESSAGES .

       LC_TIME
	      Determine  the  locale for recognizing the format of file timestamps written by the
	      diff utility in a context-difference input file.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       Not used.

STDERR
       The standard error shall be used for diagnostic and informational messages.

OUTPUT FILES
       The output of the patch utility, the save files ( .orig suffixes), and the reject files	(
       .rej suffixes) shall be text files.

EXTENDED DESCRIPTION
       A  patch file may contain patching instructions for more than one file; filenames shall be
       determined as specified in Filename Determination . When the -b option is  specified,  for
       each  patched file, the original shall be saved in a file of the same name with the suffix
       .orig appended to it.

       For each patched file, a reject file may also be created as noted in Patch  Application	.
       In the absence of a -r option, the name of this file shall be formed by appending the suf-
       fix .rej to the original filename.

   Patch File Format
       The patch file shall contain zero or more lines of header information followed by  one  or
       more  patches.  Each  patch shall contain zero or more lines of filename identification in
       the format produced by diff -c, and one or more sets of diff output, which are customarily
       called hunks.

       The patch utility shall recognize the following expression in the header information:

       Index:  pathname

	      The file to be patched is named pathname.

       If  all	lines  (including headers) within a patch begin with the same leading sequence of
       <blank>s, the patch utility shall remove this  sequence	before	proceeding.  Within  each
       patch, if the type of difference is context, the patch utility shall recognize the follow-
       ing expressions:

       *** filename timestamp

	      The patches arose from filename.

       --- filename timestamp

	      The patches should be applied to filename.

       Each hunk within a patch shall be the diff output to change a line range within the origi-
       nal  file.  The	line numbers for successive hunks within a patch shall occur in ascending
       order.

   Filename Determination
       If no file operand is specified, patch shall perform the following steps to determine  the
       filename to use:

	1. If the type of diff is context, the patch utility shall delete pathname components (as
	   specified by the -p option) from the filename on the line beginning with "***" ,  then
	   test  for  the existence of this file relative to the current directory (or the direc-
	   tory specified with the -d option). If the file exists, the patch  utility  shall  use
	   this filename.

	2. If the type of diff is context, the patch utility shall delete the pathname components
	   (as specified by the -p option) from the filename on the line beginning with  "---"	,
	   then  test  for  the  existence of this file relative to the current directory (or the
	   directory specified with the -d option). If the file exists, the patch  utility  shall
	   use this filename.

	3. If  the header information contains a line beginning with the string Index:, the patch
	   utility shall delete pathname components (as specified by the  -p  option)  from  this
	   line,  then	test for the existence of this file relative to the current directory (or
	   the directory specified with the -d option).  If the file exists,  the  patch  utility
	   shall use this filename.

	4. If an SCCS directory exists in the current directory, patch shall attempt to perform a
	   get -e SCCS/s. filename command to retrieve an editable version of the  file.  If  the
	   file exists, the patch utility shall use this filename.

	5. The	patch  utility	shall  write  a  prompt to standard output and request a filename
	   interactively from the controlling terminal (for example, /dev/tty).

   Patch Application
       If the -c, -e, or -n option is present, the  patch  utility  shall  interpret  information
       within  each  hunk  as  a  context  difference,	an ed difference, or a normal difference,
       respectively. In the absence of any of these options, the patch	utility  shall	determine
       the type of difference based on the format of information within the hunk.

       For each hunk, the patch utility shall begin to search for the place to apply the patch at
       the line number at the beginning of the hunk, plus or minus any offset  used  in  applying
       the previous hunk. If lines matching the hunk context are not found, patch shall scan both
       forwards and backwards at least 1000 bytes for a set of lines that match the hunk context.

       If no such place is found and it is a context difference, then  another	scan  shall  take
       place,  ignoring the first and last line of context. If that fails, the first two and last
       two lines of context shall be ignored and another scan shall be made.  Implementations may
       search more extensively for installation locations.

       If  no  location can be found, the patch utility shall append the hunk to the reject file.
       The rejected hunk shall be written in context-difference format regardless of  the  format
       of  the	patch file. If the input was a normal or ed-style difference, the reject file may
       contain differences with zero lines of context.	The line numbers  on  the  hunks  in  the
       reject  file  may  be  different  from the line numbers in the patch file since they shall
       reflect the approximate locations for the failed hunks in the new file rather than the old
       one.

       If  the	type  of  patch  is an ed diff, the implementation may accomplish the patching by
       invoking the ed utility.

EXIT STATUS
       The following exit values shall be returned:

	0     Successful completion.

	1     One or more lines were written to a reject file.

       >1     An error occurred.

CONSEQUENCES OF ERRORS
       Patches that cannot be correctly placed in the file shall be written to a reject file.

       The following sections are informative.

APPLICATION USAGE
       The -R option does not work with ed scripts because there is  too  little  information  to
       reconstruct the reverse operation.

       The  -p	option makes it possible to customize a patch file to local user directory struc-
       tures without manually editing the patch file. For example, if the filename in  the  patch
       file was:

	      /curds/whey/src/blurfl/blurfl.c

       Setting -p 0 gives the entire pathname unmodified; -p 1 gives:

	      curds/whey/src/blurfl/blurfl.c

       without the leading slash, -p 4 gives:

	      blurfl/blurfl.c

       and not specifying -p at all gives:

	      blurfl.c .

EXAMPLES
       None.

RATIONALE
       Some  of the functionality in historical patch implementations was not specified. The fol-
       lowing documents those features present in historical implementations that have	not  been
       specified.

       A  deleted  piece of functionality was the '+' pseudo-option allowing an additional set of
       options and a patch file operand to be given. This was seen as being insufficiently useful
       to standardize.

       In  historical  implementations, if the string "Prereq:" appeared in the header, the patch
       utility would search for the corresponding version information (the  string  specified  in
       the  header, delimited by <blank>s or the beginning or end of a line or the file) anywhere
       in the original file. This was deleted as too simplistic and insufficiently trustworthy	a
       mechanism to standardize. For example, if:

	      Prereq: 1.2

       were in the header, the presence of a delimited 1.2 anywhere in the file would satisfy the
       prerequisite.

       The following options were dropped from historical implementations of  patch  as  insuffi-
       ciently useful to standardize:

       -b     The -b option historically provided a method for changing the name extension of the
	      backup file from the default .orig. This option has been modified and  retained  in
	      this volume of IEEE Std 1003.1-2001.

       -F     The  -F  option  specified  the  number  of  lines of a context diff to ignore when
	      searching for a place to install a patch.

       -f     The -f option historically caused patch not to request additional information  from
	      the user.

       -r     The  -r  option  historically  provided a method of overriding the extension of the
	      reject file from the default .rej.

       -s     The -s option historically caused patch to work silently unless an error occurred.

       -x     The -x option historically set internal debugging flags.

       In some file system implementations, the saving of  a  .orig  file  may	produce  unwanted
       results.  In  the  case	of  12, 13, or 14-character filenames (on file systems supporting
       14-character maximum filenames), the .orig file overwrites the new file.  The reject  file
       may  also  exceed  this filename limit. It was suggested, due to some historical practice,
       that a tilde ( '~' ) suffix be used instead of .orig and some other character  instead  of
       the  .rej  suffix.  This  was rejected because it is not obvious to the user which file is
       which.  The suffixes .orig and .rej are clearer and more understandable.

       The -b option has the opposite sense in some historical implementations-do  not	save  the
       .orig  file. The default case here is not to save the files, making patch behave more con-
       sistently with the other standard utilities.

       The -w option in early proposals was changed to -l to match historical practice.

       The -N option was included because without it, a non-interactive application cannot reject
       previously  applied patches.  For example, if a user is piping the output of diff into the
       patch utility, and the user only wants to patch a file to  a  newer  version  non-interac-
       tively, the -N option is required.

       Changes	to the -l option description were proposed to allow matching across <newline>s in
       addition to just <blank>s. Since this is not historical practice, and since some  ambigui-
       ties  could  result, it is suggested that future developments in this area utilize another
       option letter, such as -L.

FUTURE DIRECTIONS
       None.

SEE ALSO
       ed , diff

COPYRIGHT
       Portions of this text are reprinted and	reproduced  in	electronic  form  from	IEEE  Std
       1003.1,	2003  Edition,	Standard  for Information Technology -- Portable Operating System
       Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003  by
       the  Institute  of  Electrical  and  Electronics Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE  and  The  Open  Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					 PATCH(P)


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