Path: utzoo!attcan!uunet!fernwood!apple!sun-barr!rutgers!mcnc!sps
From: sps@mcnc.org (Stephen Schaefer)
Newsgroups: comp.lang.perl
Subject: Wait for an output pipe?
Message-ID: <SPS.90Sep27114644@pepe.mcnc.org>
Date: 27 Sep 90 15:46:44 GMT
Sender: daemon@mcnc.org
Distribution: comp
Organization: Microelectronics Center of North Carolina
Lines: 40

My perl program is writing on a pipe that I opened:

open(RMAINTNEED,"rmaintneed @ARGV|";
open(RDIST,"|rdist -f -");
while(<RMAINTNEED>) {
	...process...;
	print RDIST "rdist commands";
}

However, when it is finished writing, it does not wait for the rdist
to finish, but exits immediately, giving me my shell prompt, after
which I start seeing progress reports from rdist.  Before reading a
lot of perl source code and seemingly irrelevant pieces of the manual,
(if a simple answer is in the man page, it ought to be mentioned under
open or wait, and it's not), I'd like someone to tell me: how do I
wait for the output pipe to finish?

Let me speculate: I shouldn't have to explicitly wait, but the
``wait'' that perl does on the output process was confused by the
termination of the process from which I'm reading my input:

open(RMAINTNEED,"rmaintneed @ARGV|";
open(RDIST,"|rdist -f -");
while(<RMAINTNEED>) {
	...process...;
	print RDIST "(rdist commands)";
}

OK, I could collect the process ID from pipe open, but then how do I
wait for that process?  Wait is not documented as taking an optional
argument.  A wait without arguments at the end of the program has
behaved as a no-op.  I'm running on VAX 4.3BSD, and we do have wait3,
although the installation script mutters at our lack of wait4 (wait4
what? :-).

Thanks,
--
	Stephen P. Schaefer, Postmaster	MCNC
	sps@mcnc.org			P.O. Box 12889
	...!mcnc!sps			RTP, NC 27709