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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 fre-
       quently, 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 pre-
	      vents 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
	      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  descrip-
       tion.   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  exam-
       ple, 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 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 num-
       ber  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, respec-
       tively.	 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  $

       The command ident extracts such markers from any file, even object code
       and dumps.  Thus, ident lets you find out which revisions of which mod-
       ules 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 identi-
       fication markers; see co(1) for details.

IDENTIFICATION

       Author: Walter F. Tichy.
       Manual Page Revision: 1.5; Release Date: 1999/08/27.
       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				  1999/08/27			   RCSINTRO(1)

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