Frozen Fish 2: PC/frozenfish_august_1995.bin/bbs/d02xx/d0296.lha/Patch/patch.doc

Text File | 1989-12-28 | 19KB | 397 lines

     PPPPAAAATTTTCCCCHHHH((((1111))))             XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((LLLLOOOOCCCCAAAALLLL))))              PPPPAAAATTTTCCCCHHHH((((1111))))



     NNNNAAAAMMMMEEEE
          patch - a program for applying a diff file to an original

     SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
          ppppaaaattttcccchhhh [options] orig patchfile [+ [options] orig]

          but usually just

          ppppaaaattttcccchhhh <patchfile

     DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
          _P_a_t_c_h will take a patch file containing any of the three
          forms of difference listing produced by the _d_i_f_f program and
          apply those differences to an original file, producing a
          patched version.  By default, the patched version is put in
          place of the original, with the original file backed up to
          the same name with the extension ".orig" or "~" , or as
          specified by the ----bbbb switch.  You may also specify where you
          want the output to go with a ----oooo switch.  If _p_a_t_c_h_f_i_l_e is
          omitted, or is a hyphen, the patch will be read from
          standard input.

          Upon startup, patch will attempt to determine the type of
          the diff listing, unless over-ruled by a ----cccc, ----eeee, or ----nnnn
          switch.  Context diffs and normal diffs are applied by the
          _p_a_t_c_h program itself, while ed diffs are simply fed to the
          _e_d editor via a pipe.

          _P_a_t_c_h will try 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 _p_a_t_c_h, and
          it should work.  If the entire diff is indented by a
          consistent amount, this will be taken into account.

          With context diffs, and to a lesser extent with normal
          diffs, _p_a_t_c_h can detect when the line numbers mentioned in
          the patch are incorrect, and will attempt 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, _p_a_t_c_h will scan both forwards
          and backwards for a set of lines matching the context given
          in the hunk.  First _p_a_t_c_h 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 factor 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 factor is 2.) If _p_a_t_c_h cannot find a
          place to install that hunk of the patch, it will put the
          hunk out to a reject file, which normally is the name of the



     Page 1                                         (printed 12/28/89)






     PPPPAAAATTTTCCCCHHHH((((1111))))             XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((LLLLOOOOCCCCAAAALLLL))))              PPPPAAAATTTTCCCCHHHH((((1111))))



          output file plus ".rej" or "#" .  (Note that the rejected
          hunk will come out in context diff form whether the input
          patch was a context diff or a normal diff.  If the input was
          a normal diff, many of the contexts will simply be 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 will be told whether the hunk
          succeeded or failed, and which line (in the new file) _p_a_t_c_h
          thought the hunk should go on.  If this is different from
          the line number specified in the diff you will be told the
          offset.  A single large offset MAY be an indication that a
          hunk was installed in the wrong place.  You will also be
          told if a fuzz factor was used to make the match, in which
          case you should also be slightly suspicious.

          If no original file is specified on the command line, _p_a_t_c_h
          will try to figure out from the leading garbage what the
          name of the file to edit is.  In the header of a context
          diff, the filename is found from lines beginning with "***"
          or "---", with the shortest name of an existing file
          winning.  Only context diffs have lines like that, but if
          there is an "Index:" line in the leading garbage, _p_a_t_c_h will
          try to use the filename from that line.  The context diff
          header takes precedence over an Index line.  If no filename
          can be intuited from the leading garbage, you will be asked
          for the name of the file to patch.

          (If the original file cannot be found, but a suitable SCCS
          or RCS file is handy, _p_a_t_c_h will attempt to get or check out
          the file.)

          Additionally, if the leading garbage contains a "Prereq: "
          line, _p_a_t_c_h will take the first word from the prerequisites
          line (normally a version number) and check the input file to
          see if that word can be found.  If not, _p_a_t_c_h will ask for
          confirmation before proceeding.

          The upshot of all this is that you should be able to say,
          while in a news interface, 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, _p_a_t_c_h will
          try 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



     Page 2                                         (printed 12/28/89)






     PPPPAAAATTTTCCCCHHHH((((1111))))             XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((LLLLOOOOCCCCAAAALLLL))))              PPPPAAAATTTTCCCCHHHH((((1111))))



          determined for each diff listing, and that the garbage
          before each diff listing will be examined for interesting
          things such as filenames and revision level, as mentioned
          previously.  You can give switches (and another original
          file name) for the second and subsequent patches by
          separating the corresponding argument lists by a '+'.  (The
          argument list for a second or subsequent patch may not
          specify a new patch file, however.)

          _P_a_t_c_h recognizes the following switches:

          ----bbbb   causes the next argument to be interpreted as the
               backup extension, to be used in place of ".orig" or
               "~".

          ----BBBB   causes the next argument to be interpreted as a prefix
               to the backup file name. If this argument is specified
               any argument from -b will be ignored.  This argument is
               an extension to Larry Wall's patch v2.0.1.4, patchlevel
               8, made by M. Greim ([e-mail]).

          ----cccc   forces _p_a_t_c_h to interpret the patch file as a context
               diff.

          ----dddd   causes _p_a_t_c_h to interpret the next argument as a
               directory, and cd to it before doing anything else.

          ----DDDD   causes _p_a_t_c_h to use the "#ifdef...#endif" construct to
               mark changes.  The argument following will be used as
               the differentiating symbol.  Note that, unlike the C
               compiler, there must be a space between the ----DDDD and the
               argument.

          ----eeee   forces _p_a_t_c_h to interpret the patch file as an ed
               script.

          ----ffff   forces _p_a_t_c_h to assume that the user knows exactly what
               he or she is doing, and to not ask any questions.  It
               does not suppress commentary, however.  Use ----ssss for
               that.

          ----FFFF<<<<nnnnuuuummmmbbbbeeeerrrr>>>>
               sets the maximum fuzz factor.  This switch only applies
               to context diffs, and causes _p_a_t_c_h 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.

          ----llll   causes the pattern matching to be done loosely, in case
               the tabs and spaces have been munged in your input



     Page 3                                         (printed 12/28/89)






     PPPPAAAATTTTCCCCHHHH((((1111))))             XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((LLLLOOOOCCCCAAAALLLL))))              PPPPAAAATTTTCCCCHHHH((((1111))))



               file.  Any sequence of whitespace in the pattern line
               will match any sequence in the input file.  Normal
               characters must still match exactly.  Each line of the
               context must still match a line in the input file.

          ----nnnn   forces _p_a_t_c_h to interpret the patch file as a normal
               diff.

          ----NNNN   causes _p_a_t_c_h to ignore patches that it thinks are
               reversed or already applied.  See also ----RRRR ....

          ----oooo   causes the next argument to be interpreted as the
               output file name.

          ----pppp<<<<nnnnuuuummmmbbbbeeeerrrr>>>>
               sets the pathname strip count, which controls how
               pathnames found in the patch file are treated, in case
               the you keep your files in a different directory than
               the person who sent out the patch.  The strip count
               specifies how many slashes are to be stripped from the
               front of the pathname.  (Any intervening directory
               names also go away.) For example, supposing the
               filename in the patch file was

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

               setting ----pppp or ----pppp0000 gives the entire pathname unmodified,
               ----pppp1111 gives

                       u/howard/src/blurfl/blurfl.c

               without the leading slash, ----pppp4444 gives

                       blurfl/blurfl.c

               and not specifying ----pppp 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 ----dddd
               switch.

          ----rrrr   causes the next argument to be interpreted as the
               reject file name.

          ----RRRR   tells _p_a_t_c_h that this patch was created with the old
               and new files swapped.  (Yes, I'm afraid that does
               happen occasionally, human nature being what it is.)
               _P_a_t_c_h will attempt to swap each hunk around before
               applying it.  Rejects will come out in the swapped
               format.  The ----RRRR switch will not work with ed diff
               scripts because there is too little information to
               reconstruct the reverse operation.




     Page 4                                         (printed 12/28/89)






     PPPPAAAATTTTCCCCHHHH((((1111))))             XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((LLLLOOOOCCCCAAAALLLL))))              PPPPAAAATTTTCCCCHHHH((((1111))))



               If the first hunk of a patch fails, _p_a_t_c_h will reverse
               the hunk to see if it can be applied that way.  If it
               can, you will be asked if you want to have the ----RRRR
               switch set.  If it can't, the patch will continue to be
               applied normally.  (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 will match anywhere.  Luckily, most
               patches add or change lines rather than delete them, so
               most reversed normal diffs will begin with a delete,
               which will fail, triggering the heuristic.)

          ----ssss   makes _p_a_t_c_h do its work silently, unless an error
               occurs.

          ----SSSS   causes _p_a_t_c_h to ignore this patch from the patch file,
               but continue on looking for the next patch in the file.
               Thus

                       patch -S + -S + <patchfile

               will ignore the first and second of three patches.

          ----vvvv   causes _p_a_t_c_h to print out it's revision header and
               patch level.

          ----xxxx<<<<nnnnuuuummmmbbbbeeeerrrr>>>>
               sets internal debugging flags, and is of interest only
               to _p_a_t_c_h patchers.

     EEEENNNNVVVVIIIIRRRROOOONNNNMMMMEEEENNNNTTTT
          No environment variables are used by _p_a_t_c_h.

     FFFFIIIILLLLEEEESSSS
          /tmp/patch*

     SSSSEEEEEEEE AAAALLLLSSSSOOOO
          diff(1)

     NNNNOOOOTTTTEEEESSSS FFFFOOOORRRR PPPPAAAATTTTCCCCHHHH SSSSEEEENNNNDDDDEEEERRRRSSSS
          There are several things you should bear in mind if you are
          going to be sending out patches.  First, 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.  Second, make sure you've specified
          the filenames right, either in a context diff header, or
          with an Index: line.  If you are patching something in a
          subdirectory, be sure to tell the patch user to specify a ----pppp
          switch as needed.  Third, you can create a file by sending



     Page 5                                         (printed 12/28/89)






     PPPPAAAATTTTCCCCHHHH((((1111))))             XXXXEEEENNNNIIIIXXXX SSSSyyyysssstttteeeemmmm VVVV ((((LLLLOOOOCCCCAAAALLLL))))              PPPPAAAATTTTCCCCHHHH((((1111))))



          out a diff that compares a null file to the file you want to
          create.  This will only work if the file you want to create
          doesn't exist already in the target directory.  Fourth, take
          care not to send out reversed patches, since it makes people
          wonder whether they already applied the patch.  Fifth, while
          you may be able to get away with putting 582 diff listings
          into one file, it is probably wiser to group related patches
          into separate files in case something goes haywire.

     DDDDIIIIAAAAGGGGNNNNOOOOSSSSTTTTIIIICCCCSSSS
          Too many to list here, but generally indicative that _p_a_t_c_h
          couldn't parse your patch file.

          The message "Hmm..." indicates that there is unprocessed
          text in the patch file and that _p_a_t_c_h is attempting to
          intuit whether there is a patch in that text and, if so,
          what kind of patch it is.

          _P_a_t_c_h will exit with a non-zero status if any reject files
          were created.  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.

     CCCCAAAAVVVVEEEEAAAATTTTSSSS
          _P_a_t_c_h cannot tell if the line numbers are off in an ed
          script, and can only detect bad line numbers in a normal
          diff when it finds a "change" or a "delete" command.  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 indication that the patch worked, but not
          always.

          _P_a_t_c_h 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.

     BBBBUUUUGGGGSSSS
          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
          OLDCODE ... #else ...  #endif), _p_a_t_c_h 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, _p_a_t_c_h will
          think it is a reversed patch, and offer to un-apply the
          patch.  This could be construed as a feature.



     Page 6                                         (printed 12/28/89)