Capturing output from a "moving" system call

DreamT has asked for the wisdom of the Perl Monks concerning the following question:

Hi,
I often make a system call by using backticks, like this:

my $output = `cat /proc/loadavg`;
print $output;
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, which works fine. But, If I want to capture the output from a "continous" application, like ping or top, how can I do that? Since these applications runs "forever" until you tell them to quit?

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Re: Capturing output from a "moving" system call by Anonymous Monk on Sep 24, 2009 at 16:45 UTC
use IPC::Run, or IPC::Open, and read one line at a time	[reply]
Re: Capturing output from a "moving" system call by hippsta (Acolyte) on Sep 24, 2009 at 17:29 UTC
Try it like this: #!/usr/bin/perl use warnings; use strict; my $cmd = 'top'; open(TOP, "-\|", "$cmd"); while (<TOP>) { print "$_"; } close (TOP); :) Respectfully, Brother Hippsta	[reply]
Re: Capturing output from a "moving" system call by saberworks (Curate) on Sep 24, 2009 at 20:01 UTC
If you just need the info from top, for example, you can just run top in logging mode with a single sample: `top -l 1` Most command line tools like top and ping can just do whatever it is then exit, you don't necessarily have to use them in interactive mode.	[reply] [d/l]