PATCH(1)                                                 PATCH(1)

NAME
       patch - apply a diff file to an original

SYNOPSIS
       patch [options] [originalfile [patchfile]]

       but usually just

       patch -pnum <patchfile

DESCRIPTION
       patch takes a patch file patchfile containing a difference
       listing produced by the diff  program  and  applies  those
       differences  to  one  or  more  original  files, producing
       patched versions.  Normally the patched versions  are  put
       in  place  of the originals.  Backups can be made; see the
       -b or --backup option.  The  names  of  the  files  to  be
       patched  are  usually  taken  from  the patch file, but if
       there's just one file to be patched it  can  specified  on
       the command line as originalfile.

       Upon  startup, patch attempts to determine the type of the
       diff listing, unless overruled by  a  -c  (--context),  -e
       (--ed),  -n (--normal), or -u (--unified) option.  Context
       diffs (old-style, new-style, and unified) and normal diffs
       are  applied  by  the patch program itself, while ed diffs
       are simply fed to the ed(1) editor via a pipe.

       patch tries to skip any leading garbage, apply  the  diff,
       and  then  skip any trailing garbage.  Thus you could feed
       an article or message containing a diff listing to  patch,
       and  it  should work.  If the entire diff is indented by a
       consistent amount, or if a context  diff  is  encapsulated
       one  or  more  times  by prepending "- " to lines starting
       with "-" as specified by Internet RFC 934, this  is  taken
       into account.

       With  context  diffs,  and  to a lesser extent with normal
       diffs, patch can detect when the line numbers mentioned in
       the  patch are incorrect, and attempts to find the correct
       place to apply each hunk of the patch.  As a first  guess,
       it  takes  the line number mentioned for the hunk, plus or
       minus any offset used in applying the previous  hunk.   If
       that  is  not the correct place, patch scans both forwards
       and backwards for a set  of  lines  matching  the  context
       given  in  the  hunk.  First patch looks for a place where
       all lines of the context  match.   If  no  such  place  is
       found,  and it's a context diff, and the maximum fuzz fac-
       tor is set to 1 or more, then  another  scan  takes  place
       ignoring  the  first  and  last  line of context.  If that
       fails, and the maximum fuzz factor is set to  2  or  more,
       the  first  two and last two lines of context are ignored,
       and another scan is made.  (The default maximum fuzz  fac-
       tor  is  2.)  If patch cannot find a place to install that
       hunk of the patch, it puts the hunk out to a reject  file,
       which  normally is the name of the output file plus a .rej
       suffix, or # if .rej would generate a file  name  that  is
       too  long  (if even appending the single character # makes
       the file name too long, then # replaces  the  file  name's
       last character).  (The rejected hunk comes out in ordinary
       context diff form regardless of the  input  patch's  form.
       If  the  input was a normal diff, many of the contexts are
       simply null.)  The line numbers on the hunks in the reject
       file may be different than in the patch file: they reflect
       the approximate location patch  thinks  the  failed  hunks
       belong in the new file rather than the old one.

       As  each  hunk  is  completed,  you  are  told if the hunk
       failed, and if so which  line  (in  the  new  file)  patch
       thought  the  hunk should go on.  If the hunk is installed
       at a different line from the line number specified in  the
       diff  you  are told the offset.  A single large offset may
       indicate that a hunk was installed  in  the  wrong  place.
       You  are  also  told if a fuzz factor was used to make the
       match, in which case you should also  be  slightly  suspi-
       cious.   If  the  --verbose  option is given, you are also
       told about hunks that match exactly.

       If no original file origfile is specified on  the  command
       line,  patch  tries to figure out from the leading garbage
       what the name of the file to edit is, using the  following
       rules.

        +o If  the  header  is that of a context diff, patch takes
          the  old  and  new  file  names  in  the  header.   Any
          /dev/null names are ignored.

        +o If  there  is an Index: line in the leading garbage and
          if either the old and new names are both absent or  the
          POSIXLY_CORRECT  environment  variable  is  set,  patch
          takes the name in the Index: line.

        +o For the purpose of the following rules, the  names  are
          considered  to  be  in  the  order  (old,  new, index),
          regardless of the order that they appear in the header.

        +o If  some of the named files exist, patch uses the first
          name if the  POSIXLY_CORRECT  environment  variable  is
          set, and the best name otherwise.

        +o If  patch  is not ignoring RCS and SCCS (see the -g num
          or --get=num option), and no named files exist  but  an
          RCS or SCCS master is found, patch uses the first named
          file with an RCS or SCCS master.

        +o If no named files exist, no  RCS  or  SCCS  master  was
          found,  some  names  are  given, POSIXLY_CORRECT is not
          set, and the patch appears to create a file, patch uses
          the  best  name  requiring  the  creation of the fewest
          directories.

        +o If no file name results from the above heuristics,  you
          are asked for the name of the file to patch.

       To  determine  the  best of a nonempty list of file names,
       patch first takes all the names with the fewest path  name
       components; of those, it then takes all the names with the
       shortest basename; of those, it then takes all the  short-
       est names; finally, it takes the first remaining name.

       Additionally,  if  the  leading garbage contains a Prereq:
       line, patch takes the first word  from  the  prerequisites
       line  (normally  a version number) and checks the original
       file to see if that word can be found.  If not, patch asks
       for confirmation before proceeding.

       The  upshot of all this is that you should be able to say,
       while in a news interface, something like the following:

          | patch -d /usr/src/local/blurfl

       and patch a file in the blurfl directory directly from the
       article containing the patch.

       If  the  patch  file  contains  more than one patch, patch
       tries to apply each of them as if they came from  separate
       patch  files.   This means, among other things, that it is
       assumed that the name of the file to patch must be  deter-
       mined  for  each diff listing, and that the garbage before
       each diff listing contains interesting things such as file
       names and revision level, as mentioned previously.

OPTIONS
       -b  or  --backup
          Make  backup  files.   That  is,  when patching a file,
          rename or copy the original  instead  of  removing  it.
          When  backing  up a file that does not exist, an empty,
          unreadable backup file is created as a  placeholder  to
          represent  the  nonexistent file.  See the -V or --ver-
          sion-control option for details about how  backup  file
          names are determined.

       --backup-if-mismatch
          Back  up  a  file  if the patch does not match the file
          exactly and if backups  are  not  otherwise  requested.
          This is the default unless the POSIXLY_CORRECT environ-
          ment variable is set.

       --no-backup-if-mismatch
          Do not back up a file if the patch does not  match  the
          file   exactly   and   if  backups  are  not  otherwise
          requested.  This is the default if the  POSIXLY_CORRECT
          environment variable is set.

       -B pref  or  --prefix=pref
          Prefix  pref  to a file name when generating its simple
          backup file name.  For example, with -B /junk/ the sim-
          ple   backup   file   name   for   src/patch/util.c  is
          /junk/src/patch/util.c.

       --binary
          Read and write all files in  binary  mode,  except  for
          standard  output  and  /dev/tty.   This  option  has no
          effect on POSIX-compliant systems.  On systems like DOS
          where  this option makes a difference, the patch should
          be generated by diff -a --binary.

       -c  or  --context
          Interpret the patch file as a ordinary context diff.

       -d dir  or  --directory=dir
          Change to the directory dir immediately,  before  doing
          anything else.

       -D define  or  --ifdef=define
          Use  the  #ifdef  ... #endif construct to mark changes,
          with define as the differentiating symbol.

       --dry-run
          Print the results of applying the patches without actu-
          ally changing any files.

       -e  or  --ed
          Interpret the patch file as an ed script.

       -E  or  --remove-empty-files
          Remove  output  files  that are empty after the patches
          have been applied.  Normally this  option  is  unneces-
          sary,  since  patch  can examine the time stamps on the
          header to determine whether a file should  exist  after
          patching.   However, if the input is not a context diff
          or if the POSIXLY_CORRECT environment variable is  set,
          patch  does  not remove empty patched files unless this
          option is given.  When patch removes a  file,  it  also
          attempts to remove any empty ancestor directories.

       -f  or  --force
          Assume  that  the  user knows exactly what he or she is
          doing, and do not  ask  any  questions.   Skip  patches
          whose  headers  do not say which file is to be patched;
          patch files even though they have the wrong version for
          the  Prereq: line in the patch; and assume that patches
          are not reversed even if they look like they are.  This
          option does not suppress commentary; use -s for that.

       -F num  or  --fuzz=num
          Set  the maximum fuzz factor.  This option only applies
          to diffs that have context, and causes patch to  ignore
          up  to that many lines in looking for places to install
          a hunk.  Note that a larger fuzz factor  increases  the
          odds  of a faulty patch.  The default fuzz factor is 2,
          and it may not be set to more than the number of  lines
          of context in the context diff, ordinarily 3.

       -g num  or  --get=num
          This  option  controls  patch's  actions when a file is
          under RCS or SCCS control, and does  not  exist  or  is
          read-only  and  matches the default version.  If num is
          positive, patch gets (or checks out) the file from  the
          revision control system; if zero, patch ignores RCS and
          SCCS and does not get the file; and if negative,  patch
          asks  the  user  whether  to get the file.  The default
          value of this option is  given  by  the  value  of  the
          PATCH_GET  environment  variable  if it is set; if not,
          the default value is zero if  POSIXLY_CORRECT  is  set,
          negative otherwise.

       --help
          Print a summary of options and exit.

       -i patchfile  or  --input=patchfile
          Read the patch from patchfile.  If patchfile is -, read
          from standard input, the default.

       -l  or  --ignore-whitespace
          Match patterns loosely, in case  tabs  or  spaces  have
          been munged in your files.  Any sequence of one or more
          blanks in the patch file matches any  sequence  in  the
          original  file,  and sequences of blanks at the ends of
          lines are ignored.  Normal characters must still  match
          exactly.   Each  line of the context must still match a
          line in the original file.

       -n  or  --normal
          Interpret the patch file as a normal diff.

       -N  or  --forward
          Ignore patches that seem  to  be  reversed  or  already
          applied.  See also -R.

       -o outfile  or  --output=outfile
          Send  output  to  outfile  instead of patching files in
          place.

       -pnum  or  --strip=num
          Strip  the  smallest  prefix  containing  num   leading
          slashes from each file name found in the patch file.  A
          sequence of one or more adjacent slashes is counted  as
          a  single slash.  This controls how file names found in
          the patch file are treated, in case you keep your files
          in  a  different directory than the person who sent out
          the patch.  For example, supposing the file name in the
          patch file was

             /u/howard/src/blurfl/blurfl.c

          setting  -p0 gives the entire file name unmodified, -p1
          gives

             u/howard/src/blurfl/blurfl.c

          without the leading slash, -p4 gives

             blurfl/blurfl.c

          and not specifying -p at all just gives  you  blurfl.c.
          Whatever  you  end  up with is looked for either in the
          current directory, or the directory specified by the -d
          option.

       -r rejectfile  or  --reject-file=rejectfile
          Put rejects into rejectfile instead of the default .rej
          file.

       -R  or  --reverse
          Assume that this patch was created with the old and new
          files swapped.  (Yes, I'm afraid that does happen occa-
          sionally,  human  nature  being  what  it  is.)   patch
          attempts  to  swap each hunk around before applying it.
          Rejects come out in the swapped format.  The -R  option
          does not work with ed diff scripts because there is too
          little information to reconstruct  the  reverse  opera-
          tion.

          If  the first hunk of a patch fails, patch reverses the
          hunk to see if it can be applied that way.  If it  can,
          you  are  asked  if you want to have the -R option set.
          If it can't, the patch continues  to  be  applied  nor-
          mally.   (Note:  this  method  cannot detect a reversed
          patch if it is a normal diff and if the  first  command
          is  an append (i.e. it should have been a delete) since
          appends always succeed, due to the  fact  that  a  null
          context matches anywhere.  Luckily, most patches add or
          change lines rather than delete them, so most  reversed
          normal diffs begin with a delete, which fails, trigger-
          ing the heuristic.)

       -s  or  --silent  or  --quiet
          Work silently, unless an error occurs.

       -t  or  --batch
          Suppress questions like -f,  but  make  some  different
          assumptions:  skip patches whose headers do not contain
          file names (the same as -f); skip patches for which the
          file  has the wrong version for the Prereq: line in the
          patch; and assume that patches  are  reversed  if  they
          look like they are.

       -T  or  --set-time
          Set  the modification and access times of patched files
          from time stamps given in context diff headers,  assum-
          ing that the context diff headers use local time.  This
          option is not recommended, because patches using  local
          time  cannot  easily  be  used  by people in other time
          zones, and because local time stamps are ambiguous when
          local clocks move backwards during daylight-saving time
          adjustments.  Instead of using  this  option,  generate
          patches  with  UTC  and  use the -Z or --set-utc option
          instead.

       -u  or  --unified
          Interpret the patch file as a unified context diff.

       -v  or  --version
          Print out patch's revision header and patch level,  and
          exit.

       -V method  or  --version-control=method
          Use  method to determine backup file names.  The method
          can also be given by the PATCH_VERSION_CONTROL (or,  if
          that's  not set, the VERSION_CONTROL) environment vari-
          able, which is overridden by this option.   The  method
          does  not  affect  whether  backup  files  are made; it
          affects only the names of any  backup  files  that  are
          made.

          The value of method is like the GNU Emacs `version-con-
          trol' variable; patch also recognizes synonyms that are
          more  descriptive.   The  valid  values  for method are
          (unique abbreviations are accepted):

          existing  or  nil
             Make numbered backups of  files  that  already  have
             them,   otherwise   simple  backups.   This  is  the
             default.

          numbered  or  t
             Make numbered backups.   The  numbered  backup  file
             name for F is F.~N~ where N is the version number.

          simple  or  never
             Make  simple  backups.   The  -B  or --prefix, -Y or
             --basename-prefix, and -z or --suffix options  spec-
             ify  the  simple backup file name.  If none of these
             options are given, then a simple  backup  suffix  is
             used;  it  is  the value of the SIMPLE_BACKUP_SUFFIX
             environment variable if set, and is .orig otherwise.

          With  numbered  or  simple  backups, if the backup file
          name is too long, the backup suffix ~ is used  instead;
          if  even appending ~ would make the name too long, then
          ~ replaces the last character of the file name.

       --verbose
          Output extra information about the work being done.

       -x num  or  --debug=num
          Set internal debugging flags of interest only to  patch
          patchers.

       -Y pref  or  --basename-prefix=pref
          Prefix  pref to the basename of a file name when gener-
          ating its simple backup file name.  For  example,  with
          -Y .del/    the    simple    backup   file   name   for
          src/patch/util.c is src/patch/.del/util.c.

       -z suffix  or  --suffix=suffix
          Use suffix as the simple backup suffix.   For  example,
          with   -z -   the   simple   backup   file   name   for
          src/patch/util.c is src/patch/util.c-.  The backup suf-
          fix  may  also be specified by the SIMPLE_BACKUP_SUFFIX
          environment  variable,  which  is  overridden  by  this
          option.

       -Z  or  --set-utc
          Set  the modification and access times of patched files
          from time stamps given in context diff headers,  assum-
          ing  that the context diff headers use Coordinated Uni-
          versal Time (UTC, often known as GMT).  Also see the -T
          or --set-time option.

          The  -Z  or --set-utc and -T or --set-time options nor-
          mally refrain from setting a file's time if the  file's
          original  time  does  not  match  the time given in the
          patch header, or if its contents do not match the patch
          exactly.   However,  if  the  -f  or  --force option is
          given, the file time is set regardless.

          Due to the limitations of  diff  output  format,  these
          options cannot update the times of files whose contents
          have not changed.  Also, if you use these options,  you
          should  remove  (e.g.  with  make clean) all files that
          depend on the patched files, so that later  invocations
          of  make  do  not  get  confused  by the patched files'
          times.

ENVIRONMENT
       PATCH_GET
          This specifies whether patch gets missing or  read-only
          files  from RCS or SCCS by default; see the -g or --get
          option.

       POSIXLY_CORRECT
          If set, patch conforms more strictly to the POSIX stan-
          dard:  it  takes  the first existing file from the list
          (old, new, index) when intuiting file names  from  diff
          headers,  it does not remove files that are empty after
          patching, it does not ask whether to get files from RCS
          or SCCS, it requires that all options precede the files
          in the command line, and it does not backup files  when
          there is a mismatch.

       SIMPLE_BACKUP_SUFFIX
          Extension  to  use for simple backup file names instead
          of .orig.

       TMPDIR, TMP, TEMP
          Directory to put temporary files  in;  patch  uses  the
          first  environment  variable  in this list that is set.
          If none are set, the default is system-dependent; it is
          normally /tmp on Unix hosts.

       VERSION_CONTROL or PATCH_VERSION_CONTROL
          Selects  version  control  style;  see the -v or --ver-
          sion-control option.

FILES
       $TMPDIR/p*
          temporary files

       /dev/tty
          controlling terminal; used to get answers to  questions
          asked of the user

SEE ALSO
       diff(1), ed(1)

       Marshall T. Rose and Einar A. Stefferud, Proposed Standard
       for    Message    Encapsulation,    Internet    RFC    934
       <URL:ftp://ftp.isi.edu/in-notes/rfc934.txt> (1985-01).

NOTES FOR PATCH SENDERS
       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 directories.  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 syntax:

          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  recipient  and  applying
       your patch to a copy of the original files.

       You  can  save  people  a lot of grief by keeping a patch-
       level.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 the  POSIXLY_CORRECT  environ-
       ment  variable  is  set 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 different 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 wonder whether they already applied the patch.

       Try  not to have your patch modify derived files (e.g. the
       file configure where there is a  line  configure:  config-
       ure.in  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  hay-
       wire.

DIAGNOSTICS
       Diagnostics  generally  indicate that patch couldn't parse
       your patch file.

       If the --verbose option is given, the message Hmm... indi-
       cates that there is unprocessed text in the patch file and
       that patch is attempting 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 success-
       fully, 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 file.

CAVEATS
       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 ownership,  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 proba-
       bly do a context diff in these cases to see if the changes
       made sense.  Of course,  compiling  without  errors  is  a
       pretty  good  indication  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.

COMPATIBILITY ISSUES
       The POSIX standard specifies behavior  that  differs  from
       patch's  traditional  behavior.   You  should  be aware of
       these differences if you must interoperate with patch ver-
       sions 2.1 and earlier, which are not POSIX-compliant.

        +o 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 equiva-
          lent to -p0.  For maximum  compatibility,  use  options
          like -p0 and -p1.

          Also,  traditional  patch  simply  counted slashes when
          stripping path prefixes; patch now counts pathname com-
          ponents.   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.

        +o In traditional patch, backups were enabled by  default.
          This  behavior  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  setting the POSIXLY_CORRECT environment
          variable.

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

        +o 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 was not
          POSIX-compliant, and had a few gotchas.  Now patch uses
          a  different,  equally  complicated  (but  better docu-
          mented) method that is optionally  POSIX-compliant;  we
          hope it has fewer gotchas.  The two methods are compat-
          ible if the file names in the context diff  header  and
          the  Index:  line are all identical after prefix-strip-
          ping.   Your  patch  is  normally  compatible  if  each
          header's  file  names  all  contain  the same number of
          slashes.

        +o When traditional patch asked the user  a  question,  it
          sent  the  question 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  ques-
          tions   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.

        +o Traditional patch  exited  with  a  status  value  that
          counted  the  number  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 trou-
          ble.

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

             -c
             -d dir
             -D define
             -e
             -l
             -n
             -N
             -o outfile
             -pnum
             -R
             -r rejectfile

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

       If code has been duplicated (for instance with #ifdef OLD-
       CODE ... #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 construed as a feature.

COPYING
       Copyright 1984, 1985, 1986, 1988 Larry Wall.
       Copyright 1997 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 ver-
       sions of this manual under  the  conditions  for  verbatim
       copying,  provided  that the entire resulting derived work
       is distributed under the  terms  of  a  permission  notice
       identical to this one.

       Permission  is granted to copy and distribute translations
       of this manual into another language, under the above con-
       ditions for modified versions, except that this permission
       notice may be included in  translations  approved  by  the
       copyright holders instead of in the original English.

AUTHORS
       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  sup-
       port.

GNU                         1997/07/16                          1