# Chapter 19. The Revision Control System

#### Contents:

Overview of Commands
Basic Operation
General RCS Specifications
Conversion Guide for SCCS Users
Alphabetical Summary of Commands

This chapter presents the following topics:

- Overview of commands

- Basic operation

- General RCS specifications

- Conversion guide for SCCS users

- Alphabetical summary of commands

As with SCCS in the preceding chapter, the Revision Control System (RCS) is designed to keep track of multiple file revisions, thereby reducing the amount of storage space needed. With RCS you can automatically store and retrieve revisions, merge or compare revisions, keep a complete history (or log) of changes, and identify revisions using symbolic keywords. RCS is believed to be more efficient than SCCS. Unlike SCCS, RCS preserves execute permission on the files it manages, and you can store binary data in RCS files.

RCS is not part of standard SVR4 or Solaris. It can be obtained from the Free Software Foundation (see http://www.gnu.org). This chapter describes RCS Version 5.7.

For more information, see Applying RCS and SCCS, listed in the Bibliography.

## 19.1. Overview of Commands

The three most important RCS commands are:

`ci` | Check in revisions (put a file under RCS control).
`co` | Check out revisions.
`rcs` | Set up or change attributes of RCS files.

Two commands provide information about RCS files:

`ident` | Extract keyword values from an RCS file.
`rlog` | Display a summary (log) about the revisions in an RCS file.

You can compare RCS files with these commands:

`merge` | Incorporate changes from two files into a third file.
`rcsdiff` | Report differences between revisions.
`rcsmerge` | Incorporate changes from two RCS files into a third RCS file.

The following commands help with configuration management. However, they are considered optional, so they are not always installed.

`rcsclean` | Remove working files that have not been changed.
`rcsfreeze` | Label the files that make up a configuration.

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