How do I check if a pid is running?

[Kragen Sitaker]

"Noah" <noah at noah.org> writes:
> Thanks, this seems to work. In fact the man page for kill
> says that signal 0 can be used to check the valifity of a pid.

Of course!  How logical!  Just the other day I was thinking, "How can
I test whether or not a process exists?"  The very first thing that
occurred to me was, "I wonder if the man page for kill(2) suggests a
way to do that?"

Not.