My friend got a great Unix reference the other day -- a $14 buy from one of those "up to 80% off" computer discount bins. No matter how hard I looked, though, I couldn't find one worth buying second hand.
Rather than spend the fifty bucks on a new Unix / Linux command reference, I decided to create my own: an edited and compiled version of the almighty manpages for 39 of the most used (and useful) Unix / Linux commands.
awk, bc, chgrp, chmod, chown, cp, cron, csh, cut,
date, df, diff, env, expr, find, grep, kill, ln, ls, make,
man, mv, nroff, od, printf, ps, script, sed, shutdown,
sleep, sort, sum, tar, tr, troff, uniq, wc, which, who
1) PDF Version 2 -- Feb 21 2001 (629 kb).
Formatted, pretty headings, pages numbered and referenced by a table of contents.
2) Text Format (681 kb)
A cleaned up version of the original manpages. Great if you want to do text searches or implement your own help system.
If you find this reference useful, please let me know.