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From: bjaspan@ATHENA.MIT.EDU (Barr3y Jaspan)
Newsgroups: comp.lang.perl
Subject: Re: Perl-Users Digest #717
Message-ID: <1991Apr27.181749.8195@uvaarpa.Virginia.EDU>
Date: 27 Apr 91 18:17:49 GMT
Sender: mmdf@uvaarpa.Virginia.EDU (Uvaarpa Mail System)
Reply-To: bjaspan@ATHENA.MIT.EDU
Organization: The Internet
Lines: 34


   From: okamoto@hpcc01.HP.COM (Jeff Okamoto)
   Subject: What do you do after you've done select(2)?
   Date: 24 Apr 91 18:46:37 GMT

   I have a question about the select(2) emulation in perl.

   There are plenty of places that explain how to set up for the call to
   select, using fileno and vec to build the bitmap.  What those same examples
   DON'T provide is a good way to determine which file handle(s) are ready for
   each operation.

Well, here is a small part of a program I wrote that uses select.
Basically, I keep track of the highest filedescriptor in the fdset
that I pass to select, and then loop through the integers testing to
see if each one is in the vector.  (This is more memory efficient
than an assoc array, probably, and not very time inefficient if you
expect most of the descriptors to be set.)

(BTW, this code is part of a "fast finger" I wrote that fingers all
the machines in @ARGV in parallel, and then plays with select to get
each answer as it comes in.)

	($nfound, $timeleft) = select($rdout = $rdset, undef, undef, 15);

	if ($timeleft == 0 || $nfound == 0) {
		printf "Timeout with $argc requests unanswered.\n";
		exit(1);
	}
	
	for ($i=0; $i <= $maxfn && $nfound; $i++) {
		next unless vec($rdout, $i, 1);

Barr3y