Question

I am trying to read unbufferd data from a pipe in Perl. For example in the program below:

open FILE,"-|","iostat -dx 10 5";
$old=select FILE;
$|=1;
select $old;
$|=1;

foreach $i (<FILE>) {
  print "GOT: $i\n";
}

iostat spits out data every 10 seconds (five times). You would expect this program to do the same. However, instead it appears to hang for 50 seconds (i.e. 10×5), after which it spits out all the data.

How can I get the to return whatever data is available (in an unbuffered manner), without waiting all the way for EOF?

P.S. I have seen numerous references to this under Windows – I am doing this under Linux.

Answer 1

#!/usr/bin/env perl

use strict;
use warnings;



open(PIPE, "iostat -dx 10 1 |")       || die "couldn't start pipe: $!";

while (my $line = <PIPE>) {
    print "Got line number $. from pipe: $line";
}

close(PIPE)                           || die "couldn't close pipe: $! $?";