bash under perl

Braynid · 11-21-2007, 09:19 AM

Hey,

I've just started working with Perl so I'm not very proficient with it. The thing is I want to use Perl to manipulate the output of some bash commands, such as:

Code:

ping -c 5 -i 0.2 -s 1024 IP.IP.IP.IP | grep received | awk '{print $4}'

From the reading I've done I managed to understand the difference between "" and '' in perl, but i can't figure out how to assign the output of bash commands to Perl variables in Perl scripts.

Thanks

cramer · 11-21-2007, 10:45 AM

You will want to use the backtick (`) instead of the single quote. You can assign the output to a variable as you would a regular string.

$variable = `command`;

mangoo · 11-21-2007, 11:04 AM

And instead of using two commands (grep + awk), you could use one:

ping ... | awk '/received/{print $4}'

Braynid · 11-21-2007, 12:17 PM

Thanks cramer, it worked like a charm.
And thanks mangoo, as I was saying I'm still learning, my scripts are not that efficient right now, but they work!

bigearsbilly · 11-22-2007, 04:36 AM

A more controlled way is
to open a command as an input stream,
like so:

Code:

#!/usr/bin/perl

open LS, "2>&1 /usr/bin/ls -l |";

while (<LS>) {

    print;
    $size += (split " ")[4];
}
print "totals = $size\n";

syg00 · 11-22-2007, 05:20 AM

C'mon billy, we're trying to ease a new convert in here mate ...

Slowly, slowly at first ...

bigearsbilly · 11-22-2007, 05:46 AM

perl -e 'print pack "H*", "736f727279210a"'

angrybanana · 11-22-2007, 02:03 PM

perl can do most things that grep/sed/awk do. So you'll usually use perl to extract/modify strings.

ex.

Code:

$variable = `ping -c 5 -i 0.2 -s 1024 127.0.0.1`;
$rec = $1 if $variable =~ /(\d+) received/;

bigearsbilly · 11-23-2007, 03:16 AM

also there is in CPAN
Net::Ping

though I have never used it,