RCSINTRO(1RCS) COMMAND REFERENCE RCSINTRO(1RCS)
NAME
rcsintro - introduction to RCS commands
DESCRIPTION
The Revision Control System (RCS) manages multiple revisions
of text 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, form letters, and
so forth).
The basic user interface is extremely simple. The novice
only needs to learn two commands: ci and co. Ci, short for
checkin, deposits the contents of a text file into an
archival file called an RCS file. An RCS file contains all
revisions of a particular text file. Co, short for
checkout, retrieves revisions from an RCS file.
Functions of RCS
• Storage and retrieval of 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.
• Maintenance of 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
checkin, 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.
• Resolution of 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.
• Maintenance of 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.
• Merging of revisions and resolution of 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.
• Release and configuration control. Revisions can be
Printed 10/17/86 1
RCSINTRO(1RCS) COMMAND REFERENCE RCSINTRO(1RCS)
assigned symbolic names and marked as released, stable,
experimental, and so forth. With these facilities,
configurations of modules can be described simply and
directly.
• Automatic identification of each revision with name,
revision number, creation time, author, and so forth.
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.
• Minimization of 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. Invoke the checkin command
ci f.c
This command creates the RCS file f.c,v, 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 checkin commands will ask
you for a log entry, which should summarize the changes that
you made.
Files ending in ,v are called RCS files (v stands for
versions); the others are called working files. To get back
the working file f.c in the previous example, use the
checkout command
co f.c
This command extracts the latest revision from f.c,v and
writes it into .f.c. You can now edit f.c and check it back
in by invoking
ci f.c
Ci increments the revision number properly. If ci complains
with the message
ci error: no lock set by <your login>
Printed 10/17/86 2
RCSINTRO(1RCS) COMMAND REFERENCE RCSINTRO(1RCS)
then your system administrator has decided to create all RCS
files with the locking attribute set to strict. In this
case, you should have locked the revision during the
previous checkout. Your last checkout should have been
co -l f.c
Of course, it is too late now to do the checkout with
locking, because you probably modified f.c already, and a
second checkout 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, and so forth.
All that locking prevents is a CHECKIN by anybody but the
locker.
If your RCS file is private, for example, 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 off the RCS file
need not have a lock for checkin; 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 3 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 checkin (in
case you want to continue editing), invoke
ci -l f.c or ci -u f.c
These commands check in f.c as usual, but perform an
implicit checkout. The first form also locks the checked in
Printed 10/17/86 3
RCSINTRO(1RCS) COMMAND REFERENCE RCSINTRO(1RCS)
revision, the second one doesn't. Thus, these options save
you one checkout operation. The first form is useful if
locking is strict, the second one if not strict. 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, and so forth, 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, and
so forth. 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 (for example, 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(5rcs).
Automatic Identification
RCS can put special strings for identification into your
source and object code. To obtain such identification, place
the marker
$Header$
into your text (for instance, inside a comment). RCS will
replace this marker with a string of the form
$Header: filename revision_number
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:
Printed 10/17/86 4
RCSINTRO(1RCS) COMMAND REFERENCE RCSINTRO(1RCS)
static char rcsid[] = "$Header$";
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 checkin. Thus, you can
maintain the complete history of your file directly inside
it. There are several additional identification markers;
see co(1rcs) for details.
CAVEATS
The maximum number of revisions that can be stored in a
single RCS file is 719. When there are more than 700
revisions in a file, a warning message is printed on the
terminal (if possible) every time an RCS command works on
the file. See the manual page for rcsfile(5rcs) for
information on what action to take in this case.
On older versions of RCS, the maximum number of revisions
that can be stored in a single RCS file is 239. No warning
is displayed on the terminal if this number is exceeded.
SEE ALSO
ci(1rcs), co(1rcs), ident(1rcs), merge(1rcs), rlog(1rcs),
rcs(1rcs), rcsdiff(1rcs), rcsmerge(1rcs), rcsfile(5rcs).
Printed 10/17/86 5
%%index%%
na:72,75;
de:147,2613;2904,2121;5169,2369;7682,2293;10119,666;
ca:10785,619;
se:11404,358;
%%index%%000000000124