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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|−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.1‐2008, 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.1‐2008,   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.1‐2008.

       −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.1‐2008, 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, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  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.unix.org/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 .