Re^2: Capturing errors from 3-arg pipe open in ActivePerl 5.020

Sorry, I feel a bit dense here, but what do I do with the PID once I have it? I get a PID regardless of whether or not the command succeeded.

pipe.pl

#!/usr/bin/perl
use 5.018;
use strict;
use warnings;

my $pid = open (my $ARTICLE, "-|", "caesar") or die "Can't start caesa
+r: $!\n$^E";

my $read = <$ARTICLE>;
say "[$read][$pid]";
[download]

Results:

perl pipe.pl
'caesar' is not recognized as an internal or external command,
operable program or batch file.
Use of uninitialized value $read in concatenation (.) or string at pip
+e.pl line 9.
[][1236]
[download]

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Re^3: Capturing errors from 3-arg pipe open in ActivePerl 5.020 by Lotus1 (Vicar) on Nov 16, 2015 at 18:53 UTC
You asked in the OP what is different about your command and why isn't the 'or die' clause working in your open command. I provided documentation that shows if you open a pipe it returns the pid instead of just non-zero or zero like with opening a file. That is the difference and the answer to your question. I wasn't telling you to do anything with the pid, only that it is the return value and the reason why your code didn't work as expected. I don't think this example should be included in the documentation for open since it doesn't work as expected for pipes.	[reply]

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Re^3: Capturing errors from 3-arg pipe open in ActivePerl 5.020
by Lotus1 (Vicar) on Nov 16, 2015 at 18:53 UTC

You asked in the OP what is different about your command and why isn't the 'or die' clause working in your open command. I provided documentation that shows if you open a pipe it returns the pid instead of just non-zero or zero like with opening a file. That is the difference and the answer to your question.

I wasn't telling you to do anything with the pid, only that it is the return value and the reason why your code didn't work as expected.

I don't think this example should be included in the documentation for open since it doesn't work as expected for pipes.

[reply]