


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
       o      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.

       o      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.

       o      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.

       o      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.

       o      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.

       o      Control releases and configurations.  Revisions can
              be assigned symbolic names and marked as released,
              stable, experimental, etc.  With these facilities,



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              configurations of modules can be described simply
              and directly.

       o      Automatically identify each revision with name,
              revision number, creation time, author, etc.  The
              identification 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
              configuration.

       o      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




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RCSINTRO(1)                                           RCSINTRO(1)


       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 people
       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),



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       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 identification,
       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



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RCSINTRO(1)                                           RCSINTRO(1)


       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.
       Revision Number: 5.2; Release Date: 1992/02/17.
       Copyright 1982, 1988, 1989 by Walter F. Tichy.
       Copyright 1990, 1991, 1992 by 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.




























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