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       patch - apply changes to files


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


       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
       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 determinable for each diff listing.)


       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

              #ifndef define

       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 difference script to match
              any sequence of <blank>s in the input  file.  Other  characters  shall  be  matched

       -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
              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 .


       The following operand shall be supported:

       file   A pathname of a file to patch.


       See the INPUT FILES section.


       Input files shall be text files.


       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 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.

              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).

              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.

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

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




       Not used.


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


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


       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 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  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  "---"  ,
           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

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


       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.


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

       The following sections are informative.


       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:


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


       without the leading slash, -p 4 gives:


       and not specifying -p at all gives:

              blurfl.c .




       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

       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 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.




       ed , diff


       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 .