Path: utzoo!mnetor!uunet!husc6!rutgers!ames!sdcsvax!ucsdhub!hp-sdd!hplabs!hpcea!hpfcdc!rml
From: rml@hpfcdc.HP.COM (Bob Lenk)
Newsgroups: comp.unix.wizards
Subject: Re: Is process <n> alive?
Message-ID: <5980013@hpfcdc.HP.COM>
Date: 17 Dec 87 21:46:50 GMT
References: <429@minya.UUCP>
Organization: HP Ft. Collins, Co.
Lines: 20

> int
> isprocess(n)
> 	int n;
> {
> 	extern int errno;
> 
> 	return (kill(n,0) == 0 || errno != ESRCH);
> }

As several people have pointed out, this approach works on System V and
recent BSD systems.  One important note is that the semantics are not
identical on those systems.  If the process in question is a zombie,
System V will tell you it exists while BSD will tell you it doesn't.

A couple of other points:  Older systems (eg. V7) don't support signal 0.
Systems meeting certain levels of security won't permit this sort of thing
in any form.

		Bob Lenk
		{ihnp4, hplabs}!hpfcla!rml