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, docu-
       mentation, 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 revi-
       sions 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 accord-
              ing 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  program-
              mers 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, 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 intermedi-
              ate 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 revi-
       sion, 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 char-
       acter 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)