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RCSINTRO(1)             FreeBSD 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 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, 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

       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: 1.5.54.1; Release Date: 2009/04/15.
       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                               2009/04/15                       RCSINTRO(1)

NAME | DESCRIPTION | IDENTIFICATION | SEE ALSO

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