ps -ef | squid will tell you if squid is actually running and gives you its PID number.
You need to put grep or egrep after the pipe and before the squid otherwise it tries to run the output of the ps through squid! ps ef | grep squid
What an idiot I am! That was a typo and it came from writing emails too late in the day. Heaven alone knows what piping the output of ps through squid would do but I'm certainly not experimenting on my system. Talking about these powerful, useful little commands, one book I've found increasingly useful is an O'Reilly one "Linux in a Nutshell - A desktop Quick Reference" by Jessica Perry Hekman and the Staff of O'Reilly and Associates; ISBN 1565921674. It covers all the core commands, costs about £15 and I'm always finding myself reaching for it. People might object that all the information it gives is already available in the man pages but I still find it very handy. Nigel.