I've started skimming through the lovely Writing shell scripts tutorial and even though I'm just in the beginning of it I've already learnt one very useful thing: the
type program. With it you can find out "what type of command it is". This is useful because sometimes you want to know where some command is coming from. I'll let this example explain its usage:
peterbe@trillian:~ $ type jed jed is /usr/bin/jed peterbe@trillian:~ $ type cvs_commit cvs_commit is /home/peterbe/bin/cvs_commit peterbe@trillian:~ $ type alias alias is a shell builtin peterbe@trillian:~ $ type sjed sjed is aliased to `sudo jed'
I'll read more of this after the weekend.