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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 differ (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) listings produced by the diff
       utility (normal, context, or in the style of ed) and apply  those  dif-
       ferences  to  a  file.  By  default, patch shall read from the standard
       input.
       The patch utility shall attempt to determine the type of the diff list-
       ing, 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
       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, out-
              file .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  con-
              structs:

              #ifdef define
              ...
              #endif

              #ifndef define
              ...
              #endif
       optionally  combined  with  the C preprocessor construct #else.  If the
       patched file is processed with the  C  preprocessor,  where  the  macro
       define  is defined, the output shall contain 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 differ-
              ence 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 ref-
              erenced 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 com-
              ponent (that is, -p 1 shall remove the leading slashes).  Speci-
              fying -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 Vari-
              ables 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 internationalization 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 arguments and input files).
       LC_MESSAGES
              Determine the locale that should be used to  affect  the  format
              and  contents  of  diagnostic messages written 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 time-
              stamps 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 mes-
       sages.
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 suffix .rej to the original file-
       name.
   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  differ-
       ence  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  file-
           name  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 util-
           ity 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 file-
           name 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  util-
           ity 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 exis-
           tence 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.
        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 inter-
       pret information within each hunk as a context difference, an  ed  dif-
       ference, 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 match-
       ing 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-differ-
       ence format regardless of the format of the patch file.  If  the  input
       was  a  normal or ed-style difference, the reject file may contain dif-
       ferences 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 exam-
       ple, 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 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 addi-
              tional 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 file-
       names (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  implementa-
       tions-do  not save the .orig file. The default case here is not to save
       the files, making patch behave more consistently with the  other  stan-
       dard 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 appli-
       cation  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 his-
       torical practice, and since some ambiguities could result, it  is  sug-
       gested  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 original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                            PATCH(1P)