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RCSINTRO(1)                                                        RCSINTRO(1)



NAME
       rcsintro - introduction to RCS commands

DESCRIPTION
       The  Revision  Control System (RCS) manages multiple revisions of files.  RCS automates the storing, retrieval,
       logging, identification, and merging of revisions.  RCS is useful for text  that  is  revised  frequently,  for
       example programs, documentation, graphics, papers, and form letters.

       The  basic  user  interface is extremely simple.  The novice only needs to learn two commands: ci(1) and co(1).
       ci, short for "check in", deposits the contents of a file into an archival file called an  RCS  file.   An  RCS
       file  contains  all revisions of a particular file.  co, short for "check out", retrieves revisions from an RCS
       file.

   Functions of RCS
       ?      Store and retrieve multiple revisions of text.  RCS saves all old revisions in a  space  efficient  way.
              Changes no longer destroy the original, because the previous revisions remain accessible.  Revisions can
              be retrieved according to ranges of revision numbers, symbolic names, dates, authors, and states.

       ?      Maintain a complete history of changes.  RCS logs all changes automatically.  Besides the text  of  each
              revision,  RCS  stores  the  author,  the  date  and time of check-in, and a log message summarizing the
              change.  The logging makes it easy to find out what happened to a  module,  without  having  to  compare
              source listings or having to track down colleagues.

       ?      Resolve access conflicts.  When two or more programmers wish to modify the same revision, RCS alerts the
              programmers and prevents one modification from corrupting the other.

       ?      Maintain a tree of revisions.  RCS can maintain separate lines  of  development  for  each  module.   It
              stores a tree structure that represents the ancestral relationships among revisions.

       ?      Merge  revisions  and resolve conflicts.  Two separate lines of development of a module can be coalesced
              by merging.  If the revisions to be merged affect the same sections of code, RCS alerts the  user  about
              the overlapping changes.

       ?      Control  releases  and configurations.  Revisions can be assigned symbolic names and marked as released,
              stable, experimental, etc.  With these facilities, configurations of modules can be described simply and
              directly.

       ?      Automatically  identify each revision with name, revision number, creation time, author, etc.  The iden-
              tification is like a stamp that can be embedded at an appropriate place in the text of a revision.   The
              identification  makes it simple to determine which revisions of which modules make up a given configura-
              tion.

       ?      Minimize secondary storage.  RCS needs little extra space for the revisions (only the differences).   If
              intermediate revisions are deleted, the corresponding deltas are compressed accordingly.

   Getting Started with RCS
       Suppose  you  have a file f.c that you wish to put under control of RCS.  If you have not already done so, make
       an RCS directory with the command

              mkdir  RCS

       Then invoke the check-in command

              ci  f.c

       This command creates an RCS file in the RCS directory, stores f.c into it as revision 1.1, and deletes f.c.  It
       also  asks you for a description.  The description should be a synopsis of the contents of the file.  All later
       check-in commands will ask you for a log entry, which should summarize the changes that you made.

       Files in the RCS directory are called RCS files; the others are called working files.  To get back the  working
       file f.c in the previous example, use the check-out command

              co  f.c

       This  command  extracts the latest revision from the RCS file and writes it into f.c.  If you want to edit f.c,
       you must lock it as you check it out with the command

              co  -l  f.c

       You can now edit f.c.

       Suppose after some editing you want to know what changes that you have made.  The command

              rcsdiff  f.c

       tells you the difference between the most recently checked-in version and the working file.  You can check  the
       file back in by invoking

              ci  f.c

       This increments the revision number properly.

       If ci complains with the message

              ci error: no lock set by your name

       then  you have tried to check in a file even though you did not lock it when you checked it out.  Of course, it
       is too late now to do the check-out with locking, because another check-out would overwrite your modifications.
       Instead, invoke

              rcs  -l  f.c

       This  command  will  lock  the latest revision for you, unless somebody else got ahead of you already.  In this
       case, you'll have to negotiate with that person.

       Locking assures that you, and only you, can check in the next update, and avoids nasty problems if several peo-
       ple  work  on the same file.  Even if a revision is locked, it can still be checked out for reading, compiling,
       etc.  All that locking prevents is a check-in by anybody but the locker.

       If your RCS file is private, i.e., if you are the only person who is going to deposit revisions into it, strict
       locking is not needed and you can turn it off.  If strict locking is turned off, the owner of the RCS file need
       not have a lock for check-in; all others still do.  Turning strict locking off and on is done with the commands

              rcs  -U  f.c     and     rcs  -L  f.c

       If  you  don't  want to clutter your working directory with RCS files, create a subdirectory called RCS in your
       working directory, and move all your RCS files there.  RCS commands will look first into that directory to find
       needed files.  All the commands discussed above will still work, without any modification.  (Actually, pairs of
       RCS and working files can be specified in three ways: (a) both are given, (b) only the working file  is  given,
       (c) only the RCS file is given.  Both RCS and working files may have arbitrary path prefixes; RCS commands pair
       them up intelligently.)

       To avoid the deletion of the working file during check-in (in case you want to continue editing or  compiling),
       invoke

              ci  -l  f.c     or     ci  -u  f.c

       These commands check in f.c as usual, but perform an implicit check-out.  The first form also locks the checked
       in revision, the second one doesn't.  Thus, these options save you one check-out operation.  The first form  is
       useful  if  you  want  to  continue editing, the second one if you just want to read the file.  Both update the
       identification markers in your working file (see below).

       You can give ci the number you want assigned to a checked in revision.  Assume all your revisions were numbered
       1.1, 1.2, 1.3, etc., and you would like to start release 2.  The command

              ci  -r2  f.c     or     ci  -r2.1  f.c

       assigns  the  number  2.1 to the new revision.  From then on, ci will number the subsequent revisions with 2.2,
       2.3, etc.  The corresponding co commands

              co  -r2  f.c     and     co  -r2.1  f.c

       retrieve the latest revision numbered 2.x and the revision 2.1, respectively.  co  without  a  revision  number
       selects  the  latest  revision  on the trunk, i.e. the highest revision with a number consisting of two fields.
       Numbers with more than two fields are needed for branches.  For example, to start a  branch  at  revision  1.3,
       invoke

              ci  -r1.3.1  f.c

       This  command  starts  a branch numbered 1 at revision 1.3, and assigns the number 1.3.1.1 to the new revision.
       For more information about branches, see rcsfile(5).

   Automatic Identification
       RCS can put special strings for identification into your source and object code.  To  obtain  such  identifica-
       tion, place the marker

              $Id$

       into your text, for instance inside a comment.  RCS will replace this marker with a string of the form

              $Id:  filename  revision  date  time  author  state  $

       With  such  a  marker on the first page of each module, you can always see with which revision you are working.
       RCS keeps the markers up to date automatically.  To propagate the markers into your  object  code,  simply  put
       them into literal character strings.  In C, this is done as follows:

              static char rcsid[] = "$Id$";

       The  command  ident extracts such markers from any file, even object code and dumps.  Thus, ident lets you find
       out which revisions of which modules were used in a given program.

       You may also find it useful to put the marker $Log$ into your text, inside a comment.  This marker  accumulates
       the  log messages that are requested during check-in.  Thus, you can maintain the complete history of your file
       directly inside it.  There are several additional identification markers; see co(1) for details.

IDENTIFICATION
       Author: Walter F. Tichy.
       Manual Page Revision: 5.3; Release Date: 1993/11/03.
       Copyright (C) 1982, 1988, 1989 Walter F. Tichy.
       Copyright (C) 1990, 1991, 1992, 1993 Paul Eggert.

SEE ALSO
       ci(1), co(1), ident(1), rcs(1), rcsdiff(1), rcsintro(1), rcsmerge(1), rlog(1)
       Walter F. Tichy, RCS--A System for Version Control, Software--Practice & Experience 15, 7 (July 1985), 637-654.



GNU                               1993/11/03                       RCSINTRO(1)