RCS: Why and How

• get easy access to all previous versions of files to
  • undo unfortunate modifications,
  • reconstruct the source code of old file versions;
• get easy access to a list of changes (diff) that have been made to the files;
• get experience using a revision control system without the complexities of more advanced systems.

RCS consists of the four frequently used shell commands ci, co, rlog, and rcsdiff, as well as of the rarely needed commands rcs, ident, rcsclean, and rcsmerge.   Read man rcsintro to get a quick overview of the system. Basically all you have to remember is:

ci -l filename

Upload your latest changes back into the database, but do not release the lock and keep a writable working file.
(Without option -l, ci would remove the file you're working on and you'd have to use co to get it back.)

ci -u filename

Upload (check in) your latest changes back into the database, release your lock, and keep a read-only copy of the file.
(Without option -u, ci would remove your working file and you'd have to use co to get it back.)

co filename

Retrieve (check out) an unlocked latest-version read-only working file from the database.

co -l filename

Retrieve a locked latest-version writable working file from the database. Only one user can have such a writable locked version at a time.

rlog filename

Show the revision history of a file.

rcsdiff filename

Show the differences between your working file and the latest revision in the database.

The primary owner of a file creates a subdirectory RCS/ in the directory where their files to be managed are located. In this directory, the RCS commands will keep a filename,v database file associated with your working file. This database file will contain the entire revision history of one of your files.

See the man pages of each command for more information.

NOTE: RCS offers version control only for individual files and provides no support for remote access. Its facilities for collaborative work are quite restricted. It has no notion of directory trees and changes to them (e.g., copying or renaming files and directories). For any project that consists of more than a very small number of files or that has subdirectories or multiple people working on it, RCS is no longer considered an appropriate choice. The Subversion system (see manual) is a sophisticated revision control system that can handle these advanced conditions.

This handout based on http://www.cl.cam.ac.uk/~mgk25/rcsintro.html by Markus Kuhn.