A little starting point:

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

print "Starting external program. Waiting for input.\n";
open my $fh, "-|", "while true; do date; sleep 1; done";
my @lines;
while(defined(my $line = <$fh>)) {
    chomp $line;
    push @lines, $line;
    if(@lines >= 20) {
        my $howmuch = @lines;
        print "Read '$howmuch' lines from external program.\n";
        print "Stats are...calc calc calc.\n";
        print "The following lines where read:\n";
        print map { "$_\n"; } splice @lines;
        print "Going to sleep.\n";
        sleep 20;
    }
}

[download]

Looking at the docs of the used commands should push you forward. Search here helps also (reading from external program, capturing from external program).

Best regards
McA

In reply to Re: Help with fork, read and write from a pipe by McA
in thread Help with fork, read and write from a pipe by h123

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