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PATCH(1P)                  POSIX Programmer's Manual                 PATCH(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

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) list-
       ings 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 standard input.

       The  patch utility shall attempt to determine the type of the diff listing, unless overruled 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 deter-
       minable 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 processed with the C pre-
       processor, where the macro define is defined, the output shall contain the changes from the patch file;  other-
       wise, 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 lead-
              ing 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 successfully
              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, Internationalization Variables for  the  prece-
              dence 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 internationalization variables.

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

       LC_MESSAGES
              Determine  the locale that should be used to affect the format and contents of diagnostic messages writ-
              ten to standard error and informative messages written to standard 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 con-
              text-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  speci-
       fied  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 suffix .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 following 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 original 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 rela-
           tive to the current directory (or the directory 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. file-
           name 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 structures  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 following 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 insufficiently useful  to  stan-
       dardize:

       -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 consistently 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-interactively, 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 ambiguities 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, Stan-
       dard  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  original  Standard
       can be obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                            PATCH(1P)