rcs

Revision Control System for file versioning

TLDR

Initialize RCS for a file (check in initial version)

$ ci [filename]

Check out a file for editing (locked)

$ co -l [filename]

Check out a read-only copy

$ co [filename]

Check in changes with a log message

$ ci -m "[message]" [filename]

View revision history

$ rlog [filename]

Show differences between working file and latest revision

$ rcsdiff [filename]

Check out a specific revision

$ co -r[1.2] [filename]

SYNOPSIS

rcs [options] file...ci [options] file...co [options] file...

RCS (Revision Control System) manages multiple revisions of files, providing version control for individual files. It automates storing, retrieving, logging, and merging revisions, making it useful for source code, documentation, and configuration files.The workflow centers on ci (check-in) and co (check-out). Check-in stores a new revision and removes the working file by default. Check-out retrieves a revision; use -l to lock the file for exclusive editing.RCS stores revisions efficiently using reverse deltas—the latest revision is stored complete, while older revisions are stored as differences. This makes retrieving the current version fast.Revisions are numbered hierarchically (1.1, 1.2, 1.3, etc.). The first number is the release, the second is the level. Branches create additional number fields (1.2.1.1).

PARAMETERS

ci (check-in)

Store a new revision in the RCS file

co (check-out)

Retrieve a revision from the RCS file

rcs

Change RCS file attributes

rcsdiff

Compare RCS revisions

rcsmerge

Merge RCS revisions

rlog

Print revision log messages

-l

Lock the revision for exclusive editing (with co)

-u

Unlock after check-in (with ci)

-rrev

Specify revision number

-mmsg

Specify log message

-q

Quiet mode, suppress diagnostics

-ddate

Select the latest revision on or before the given date (with co)

-wlogin

Select the latest revision checked in by the given user (with co)

-ksub

Set keyword substitution mode (e.g., -kv, -kvl, -ko)

INSTALL

sudo apt install rcs

sudo dnf install rcs

sudo pacman -S rcs

sudo apk add rcs

sudo zypper install rcs

brew install rcs

nix profile install nixpkgs#rcs

CAVEATS

RCS operates on individual files, not directories or projects. For multi-file version control, modern tools like Git are more appropriate.The default check-in behavior removes the working file. Use ci -u to keep an unlocked copy or ci -l to keep a locked copy for continued editing.RCS files (ending in ,v) are stored in the same directory or in an RCS/ subdirectory. Ensure proper permissions for collaborative use.

HISTORY

RCS was developed by Walter F. Tichy at Purdue University, first released in 1982. It was one of the earliest version control systems and influenced later tools like CVS (which added network support) and eventually Git. RCS is part of the GNU project and continues to be available on most Unix-like systems.

rcs