PATCH linux command manual

PATCH(1)                                                           PATCH(1)

       patch - apply a diff file to an original

       patch [options] [originalfile [patchfile]]

       but usually just

       patch -pnum  (1985-01).

       There  are  several things you should bear in mind if you are going to
       be sending out patches.

       Create your patch  systematically.   A  good  method  is  the  command
       diff -Naur old new where old and new identify the old and new directo-
       ries.  The names old and new should not contain any slashes.  The diff
       command's  headers should have dates and times in Universal Time using
       traditional Unix format, so that patch recipients can use  the  -Z  or
       --set-utc  option.   Here  is  an  example command, using Bourne shell

          LC_ALL=C TZ=UTC0 diff -Naur gcc-2.7 gcc-2.8

       Tell your recipients how to apply the  patch  by  telling  them  which
       directory to cd to, and which patch options to use.  The option string
       -Np1 is recommended.  Test your procedure by pretending to be a recip-
       ient and applying your patch to a copy of the original files.

       You  can  save  people  a  lot of grief by keeping a patchlevel.h file
       which is patched to increment the patch level as the first diff in the
       patch file you send out.  If you put a Prereq: line in with the patch,
       it won't let them apply patches out of order without some warning.

       You can create a file by sending out a diff that compares /dev/null or
       an  empty  file  dated the Epoch (1970-01-01 00:00:00 UTC) to the file
       you want to create.  This only works if the file you  want  to  create
       doesn't  exist  already  in the target directory.  Conversely, you can
       remove a file by sending out a context diff that compares the file  to
       be  deleted  with  an  empty  file  dated the Epoch.  The file will be
       removed  unless  patch  is  conforming  to  POSIX  and   the   -E   or
       --remove-empty-files  option  is  not  given.  An easy way to generate
       patches that create and remove files  is  to  use  GNU  diff's  -N  or
       --new-file option.

       If the recipient is supposed to use the -pN option, do not send output
       that looks like this:

          diff -Naur v2.0.29/prog/README prog/README
          --- v2.0.29/prog/README   Mon Mar 10 15:13:12 1997
          +++ prog/README   Mon Mar 17 14:58:22 1997

       because the two file names have different numbers of slashes, and dif-
       ferent  versions  of  patch  interpret the file names differently.  To
       avoid confusion, send output that looks like this instead:

          diff -Naur v2.0.29/prog/README v2.0.30/prog/README
          --- v2.0.29/prog/README   Mon Mar 10 15:13:12 1997
          +++ v2.0.30/prog/README   Mon Mar 17 14:58:22 1997

       Avoid sending patches that compare backup file names like README.orig,
       since  this might confuse patch into patching a backup file instead of
       the real file.  Instead, send patches that compare the same base  file
       names in different directories, e.g. old/README and new/README.

       Take care not to send out reversed patches, since it makes people won-
       der whether they already applied the patch.

       Try not to have your patch modify derived files (e.g. the file config-
       ure  where  there is a line configure: in your makefile),
       since the recipient should be able to  regenerate  the  derived  files
       anyway.   If  you must send diffs of derived files, generate the diffs
       using UTC, have  the  recipients  apply  the  patch  with  the  -Z  or
       --set-utc option, and have them remove any unpatched files that depend
       on patched files (e.g. with make clean).

       While you may be able to get away with putting 582 diff listings  into
       one file, it may be wiser to group related patches into separate files
       in case something goes haywire.

       Diagnostics generally indicate that patch couldn't  parse  your  patch

       If  the  --verbose  option is given, the message Hmm... indicates that
       there is unprocessed text in the patch file and that patch is attempt-
       ing  to  intuit whether there is a patch in that text and, if so, what
       kind of patch it is.

       patch's exit status is 0 if all hunks are applied successfully,  1  if
       some  hunks cannot be applied, and 2 if there is more serious trouble.
       When applying a set of patches in a loop it behooves you to check this
       exit  status  so  you don't apply a later patch to a partially patched

       Context diffs cannot reliably represent the creation  or  deletion  of
       empty  files,  empty  directories,  or  special files such as symbolic
       links.  Nor can they represent changes to file  metadata  like  owner-
       ship,  permissions, or whether one file is a hard link to another.  If
       changes like these are also required, separate  instructions  (e.g.  a
       shell script) to accomplish them should accompany the patch.

       patch cannot tell if the line numbers are off in an ed script, and can
       detect bad line numbers in a normal diff only when it finds  a  change
       or  deletion.   A  context  diff using fuzz factor 3 may have the same
       problem.  Until a suitable interactive interface is added, you  should
       probably  do  a context diff in these cases to see if the changes made
       sense.  Of course, compiling without errors is a pretty  good  indica-
       tion that the patch worked, but not always.

       patch  usually  produces the correct results, even when it has to do a
       lot of guessing.  However, the results are guaranteed  to  be  correct
       only when the patch is applied to exactly the same version of the file
       that the patch was generated from.

       The POSIX standard specifies behavior that differs from patch's tradi-
       tional behavior.  You should be aware of these differences if you must
       interoperate with patch versions 2.1 and earlier, which do not conform
       to POSIX.

        ? In  traditional  patch, the -p option's operand was optional, and a
          bare -p was equivalent to -p0.   The  -p  option  now  requires  an
          operand,  and  -p 0 is now equivalent to -p0.  For maximum compati-
          bility, use options like -p0 and -p1.

          Also, traditional patch simply counted slashes when stripping  path
          prefixes;  patch  now  counts  pathname  components.   That  is,  a
          sequence of one or more adjacent slashes now  counts  as  a  single
          slash.   For  maximum portability, avoid sending patches containing
          // in file names.

        ? In traditional patch, backups were enabled by default.  This behav-
          ior is now enabled with the -b or --backup option.

          Conversely, in POSIX patch, backups are never made, even when there
          is a mismatch.  In GNU patch, this behavior  is  enabled  with  the
          --no-backup-if-mismatch  option, or by conforming to POSIX with the
          --posix option or by setting the POSIXLY_CORRECT environment  vari-

          The  -b suffix  option  of  traditional  patch is equivalent to the
          -b -z suffix options of GNU patch.

        ? Traditional patch used a complicated (and incompletely  documented)
          method  to intuit the name of the file to be patched from the patch
          header.  This method did not  conform  to  POSIX,  and  had  a  few
          gotchas.  Now patch uses a different, equally complicated (but bet-
          ter documented) method that is optionally POSIX-conforming; we hope
          it  has  fewer gotchas.  The two methods are compatible if the file
          names in the context diff header and the Index: line are all  iden-
          tical after prefix-stripping.  Your patch is normally compatible if
          each header's file names all contain the same number of slashes.

        ? When traditional patch asked the user a question, it sent the ques-
          tion to standard error and looked for an answer from the first file
          in the following list that was a terminal: standard error, standard
          output, /dev/tty, and standard input.  Now patch sends questions to
          standard output and gets answers from /dev/tty.  Defaults for  some
          answers have been changed so that patch never goes into an infinite
          loop when using default answers.

        ? Traditional patch exited with a status value that counted the  num-
          ber  of bad hunks, or with status 1 if there was real trouble.  Now
          patch exits with status 1 if some hunks failed, or with 2 if  there
          was real trouble.

        ? Limit  yourself  to the following options when sending instructions
          meant to be executed  by  anyone  running  GNU  patch,  traditional
          patch,  or  a patch that conforms to POSIX.  Spaces are significant
          in the following list, and operands are required.

             -d dir
             -D define
             -o outfile
             -r rejectfile

       Please report bugs via email to .

       patch could be smarter about partial matches, excessively deviant off-
       sets and swapped code, but that would take an extra pass.

       If  code  has  been  duplicated  (for instance with #ifdef OLDCODE ...
       #else ... #endif), patch is incapable of patching both versions,  and,
       if it works at all, will likely patch the wrong one, and tell you that
       it succeeded to boot.

       If you apply a patch you've already applied,  patch  thinks  it  is  a
       reversed  patch, and offers to un-apply the patch.  This could be con-
       strued as a feature.

       Copyright 1984, 1985, 1986, 1988 Larry Wall.
       Copyright 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,  1997,  1998
       Free Software Foundation, Inc.

       Permission  is  granted to make and distribute verbatim copies of this
       manual provided the copyright notice and this  permission  notice  are
       preserved on all copies.

       Permission is granted to copy and distribute modified versions of this
       manual under the conditions for verbatim copying,  provided  that  the
       entire resulting derived work is distributed under the terms of a per-
       mission notice identical to this one.

       Permission is granted to copy and distribute translations of this man-
       ual  into  another  language,  under the above conditions for modified
       versions, except that this permission notice may be included in trans-
       lations  approved  by the copyright holders instead of in the original

       Larry Wall wrote the original version of patch.  Paul  Eggert  removed
       patch's arbitrary limits; added support for binary files, setting file
       times, and deleting files; and made it conform better to POSIX.  Other
       contributors  include  Wayne  Davison,  who added unidiff support, and
       David MacKenzie, who added configuration and backup support.

GNU                               1998/03/21                         PATCH(1)