where do files get their variables from?

[Val Schuman]

where do files like /etc/issue.net (or any other file like motd) get their variables, like %h (host name)? and how do i find out what variables i can use?

[X_console]

From the shell I would guess. Try doing a 'man bash'. It's really lenghty by the way, but it should answer some, if not all of your questions.