Manpage of RCSINTRO (1)
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Section: User Commands (1)
Updated: 1993/11/03Index of "Manpage of RCSINTRO (1)"
rcsintro - introduction to RCS commands
The Revision Control System (RCS
) manages multiple revisions of files.
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:
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.
short for ``check out'', retrieves revisions from an RCS file.
Functions of RCS
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
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.
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.
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.
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.
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.
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.
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
that you wish to put under control of RCS
If you have not already done so, make an RCS
directory with the command
Then invoke the check-in command
This command creates an RCS file in the
into it as revision 1.1, and
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
in the previous example, use the check-out
This command extracts the latest revision from the RCS file
If you want to edit
you must lock it as you check it out with the command
co -l f.c
You can now edit
Suppose after some editing you want to know what changes that you have made.
tells you the difference between the most recently checked-in version
and the working file.
You can check the file back in by invoking
This increments the revision number properly.
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
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
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
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
(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
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
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.
ci -r2 f.c or ci -r2.1 f.c
assigns the number 2.1 to the new revision.
From then on,
will number the subsequent revisions
with 2.2, 2.3, etc. The corresponding
co -r2 f.c and co -r2.1 f.c
retrieve the latest revision numbered
and the revision 2.1,
without a revision number selects
the latest revision on the
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 220.127.116.11 to the new revision. For more information about
can put special strings for identification into your source and object
code. To obtain such identification, place the marker
$Id: rcsintro.1.en.jsp,v 1.1 2017/02/14 23:48:25 gabriele Exp $
into your text, for instance inside a comment.
RCS will replace this marker with a string of the form
$Id: rcsintro.1.en.jsp,v 1.1 2017/02/14 23:48:25 gabriele Exp $
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: rcsintro.1.en.jsp,v 1.1 2017/02/14 23:48:25 gabriele Exp $";
extracts such markers from any file, even object code
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: rcsintro.1.en.jsp,v $
Revision 1.1 2017/02/14 23:48:25 gabriele
*jspf link permettono piu' colonne
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
Author: Walter F. Tichy.
Manual Page Revision: 5.3; Release Date: 1993/11/03.
Copyright © 1982, 1988, 1989 Walter F. Tichy.
Copyright © 1990, 1991, 1992, 1993 Paul Eggert.
ci(1), co(1), ident(1), rcs(1), rcsdiff(1), rcsmerge(1), rlog(1)
▤ Walter F. Tichy,
RCS--A System for Version Control,
Software--Practice & Experience
7 (July 1985), 637-654.
- Functions of RCS
- Getting Started with RCS
- Automatic Identification
- SEE ALSO