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RCSINTRO(1)							   RCSINTRO(1)

       rcsintro	- introduction to RCS commands

       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
	      the revisions (only the differences).  If	intermediate revisions
	      are deleted, the corresponding  deltas  are  compressed  accord-

   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  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 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.	 Turn-
       ing 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 num-
       ber  the	subsequent revisions with 2.2, 2.3, etc.  The corresponding co

	      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  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


       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 fol-

	      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 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.

       Author: Walter F. Tichy.
       Manual Page Revision: 50472; Release Date: 1999-08-27.
       Copyright (C) 1982, 1988, 1989 Walter F.	Tichy.
       Copyright (C) 1990, 1991, 1992, 1993 Paul Eggert.

       ci(1), co(1), ident(1), rcs(1), rcsdiff(1),  rcsintro(1),  rcsmerge(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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