Unix in a Nutshell, 4th Edition

Keyword Substitution

RCS lets you place keyword variables in your working files. These variables are later expanded into revision notes. You can then use the notes either as embedded comments in the input file or as text strings that appear when the output is printed. To create revision notes via keyword substitution , follow this procedure:

1. In your working file, type any of the keywords listed below.

2. Check the file in.

3. Check the file out again. Upon checkout, the co command expands each keyword to include its value. That is, co replaces instances of:

                   $
                   keyword
                   $

   with:

   $keyword:value$.

4. Subsequent check-in and check-out of a file updates any existing keyword values. Unless otherwise noted below, existing values are replaced by new values.

Many commands have a -k option that provides considerable flexibility during keyword substitution.