OT: Script to add line to file if it doesn't exist

[Kent West <westk@acu.edu>]

I'm asking you folks, 'cause y'all know this stuff (I've been wrestling 
with this simple task all day).

I've got a text file; I just want a script (a one-liner sed or awk 
command, etc, would be awesome) to check to see if the file contains a 
certain line of text, and if not, to add that line at the bottom of the 
file.

For example, say the file has these four lines in it:

john
mary
fred
martin

I want a script that will read the file and look for the name "fred", 
and if it's found, leave the file alone, but if it's not found, to add 
the name "fred" to the bottom of the file.

Any help appreciated. Thanks!

--
Kent West        <")))><
http://kentwest.blogspot.com