RCSINTRO(1)                                                   General Commands Manual                                                  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  hap-
              pened 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 rep-
              resents 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, 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 revi-
              sions 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

       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), 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 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)