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19.2 Basic Operation

Normally, you maintain RCS files in a subdirectory called RCS , so the first step in using RCS should be:

mkdir RCS

Next, you place an existing file (or files) under RCS control by running the check-in command:



This creates a file called file ,v in the RCS directory. file ,v is called an RCS file, and it stores all future revisions of file . When you run ci on a file for the first time, you are prompted to describe the contents. ci then deposits file into the RCS file as revision 1.1.

To edit a new revision, check out a copy:

co -l 


This causes RCS to extract a copy of file from the RCS file. You must lock the file with -l to make it writable by you. This copy is called a working file. When you're done editing, you can record the changes by checking the working file back in again:



This time, you are prompted to enter a log of the changes made, and the file is deposited as revision 1.2. Note that a check-in normally removes the working file. To retrieve a read-only copy, do a check-out without a lock:



This is useful when you need to keep a copy on hand for compiling or searching. As a shortcut to the previous ci /co , you could type:

ci -u 


This checks in the file but immediately checks out a read-only ("unlocked") copy. In practice, you would probably make a "checkpoint" of your working version and then keep going, like this:

ci -l


This checks in the file, and then checks it back out again, locked, for continued work. To compare changes between a working file and its latest revision, you can type:



Another useful command is rlog , which shows a summary of log messages. System administrators can use the rcs command to set up default behavior of RCS.

Previous: 19.1 Overview of Commands UNIX in a Nutshell: System V Edition Next: 19.3 General RCS Specifications
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