To include a keyword string you simply include the relevant text string, such as $Id$, inside the file, and commit the file. cvsnt will automatically expand the string as part of the commit operation.
It is common to embed the $Id$ string in the source files so that it gets passed through to generated files. For example, if you are managing computer program source code, you might include a variable which is initialized to contain that string. Or some C compilers may provide a #pragma ident directive. Or a document management system might provide a way to pass a string through to generated files.
The ident command (which is part of the rcs package) can be used to extract keywords and their values from a file. This can be handy for text files, but it is even more useful for extracting keywords from binary files.
$ ident samp.c samp.c: $Id$ $ gcc samp.c $ ident a.out a.out: $Id: cvs.dbk,v 18.104.22.168 2004/04/16 14:14:42 tmh Exp $
Sccs is another popular revision control system. It has a command, what, which is very similar to ident and used for the same purpose. Many sites without rcs have sccs. Since what looks for the character sequence @(#) it is easy to include keywords that are detected by either command. Simply prefix the keyword with the magic sccs phrase, like this:
static char *id="@(#) $Id$";