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RCSINTRO(1) USER COMMANDS 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, docu-
mentation, 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, sym-
bolic names, dates, authors, and states.
o+ Maintain a complete history of changes. RCS logs all
changes automatically. Besides the text of each revi-
sion, 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 pro-
grammers 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 over-
lapping changes.
o+ Control releases and configurations. Revisions can be
assigned symbolic names and marked as released, stable,
experimental, etc. With these facilities,
GNU Last change: 1991/04/21 1
RCSINTRO(1) USER COMMANDS RCSINTRO(1)
configurations of modules can be described simply and
directly.
o+ Automatically identify each revision with name, revi-
sion number, creation time, author, etc. The identifi-
cation is like a stamp that can be embedded at an
appropriate place in the text of a revision. The iden-
tification 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 con-
trol 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 summar-
ize 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
GNU Last change: 1991/04/21 2
RCSINTRO(1) USER COMMANDS RCSINTRO(1)
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 _y_o_u_r _n_a_m_e
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 _c_h_e_c_k-_i_n by anybody but the locker.
If your RCS file is private, i.e., if you are the only per-
son who is going to deposit revisions into it, strict lock-
ing is not needed and you can turn it off. If strict lock-
ing 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
GNU Last change: 1991/04/21 3
RCSINTRO(1) USER COMMANDS RCSINTRO(1)
ci -l f.c or ci -u f.c
These commands check in f.c as usual, but perform an impli-
cit 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 mark-
ers 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 com-
mand
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 th