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       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|-u] [-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 four forms of difference (diff)
       listings produced by the diff utility (normal, copied context, unified 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,
       -n, or -u 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  POSIX.1‐2017,  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 copied 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 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> characters in the difference script to match
                 any sequence of <blank> characters 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 <slash> characters shall be considered the first component (that is, -p 1
                 shall remove the leading <slash> characters). 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.

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

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  POSIX.1‐2017,  Section  8.2,  Internationalization  Variables  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_COLLATE
                 Determine  the  locale  for  the  behavior  of ranges, equivalence classes, and multi-character
                 collating elements used in the extended regular  expression  defined  for  the  yesexpr  locale
                 keyword in the LC_MESSAGES category.

       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),
                 and  the  behavior of character classes used in the extended regular expression defined for the
                 yesexpr locale keyword in the LC_MESSAGES category.

       LC_MESSAGES
                 Determine the locale used to process affirmative responses, and the locale used to  affect  the
                 format and contents of diagnostic messages and prompts written to standard error.

       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  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 the  -c,
       -C,  -u,  or  -U  options of the diff utility, 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>
       characters,  the  patch  utility  shall remove this sequence before proceeding. Within each patch, if the
       type of difference is common 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.

       If the type  of  difference  is  unified  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 "***" (if copied context)  or  "---"  (if
           unified  context), 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.

        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 "---" (if copied context) or "+++" (if
           unified context), 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, -n, or -u option is present, the patch utility shall  interpret  information  within  each
       hunk  as  a  copied  context  difference,  an  ed  difference,  a normal difference, or a unified context
       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. A rejected  hunk
       that is a copied context difference, an ed difference, or a normal difference shall be written in copied-
       context-difference  format  regardless  of  the  format  of  the patch file. It is implementation-defined
       whether a rejected hunk that is a unified context  difference  is  written  in  copied-context-difference
       format  or  in  unified-context-difference format.  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> characters 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
                 POSIX.1‐2017.

       -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> characters in
       addition to just <blank> characters. 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.

       The -u option of GNU patch has been added, along with support for unified context formats.

FUTURE DIRECTIONS

       None.

SEE ALSO

       diff, ed

       The Base Definitions volume of POSIX.1‐2017, Chapter 8,  Environment  Variables,  Section  12.2,  Utility
       Syntax Guidelines

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                         PATCH(1POSIX)