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

Hi monks, i have a question: I have a perl script that is calling many other scripts. My perl code is something like that: 

lots of things here
.....
system ("aPerlScript.pl 1 2");
.....

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At this point aPerlScript.pl starts with inputs 1 and 2, does a lot of stuff, and it again prints a lot of stuff on the screen. Now i want to have them on the screen but i also want to have them on a log file. if i use: 
my $output = `aPerlScript.pl 1 2`;
print "$output  \n";
logToSomeFile "$output"; #this is a sub routine that prints to file.

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i can get them on screen and file but it is delayed a lot. aPerlScript.pl keeps running for 3-4 minutes, and lets say prints 100 rows on screen every now and then. if i use backticks to capture it, script seems to stuck during that duration, doing nothing at all, and once aPerlScript.pl completes its work, i suddenly get 3982498234 rows show on display. How can i solve that problem? TL;DR: How can i get the same output of a script that is called from another script on both screen and a log file simultaniosly?

Replies are listed 'Best First'.
Re: script and its output on different handles
by choroba (Cardinal) on Nov 28, 2013 at 10:39 UTC
    Not tested: 
    open my $SCRIPT, 'aPerlScript.pl 1 2 |' or die $!;
while (<$SCRIPT>) {
    print;
    log($logfile, $_);
}

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    لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
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Re: script and its output on different handles
by hdb (Monsignor) on Nov 28, 2013 at 10:39 UTC

    At least on Unix, there is a utility called tee which helps you to print to the screen and to a file simultaneously.

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Re: script and its output on different handles
by drmrgd (Beadle) on Nov 28, 2013 at 13:03 UTC
    I've used IO::Tee to do this kind of thing in the past. In short, you use the module to create a file handle pointing to your log file and STDOUT kind of like this: 
    use warnings;
use strict;
use IO::Tee;

open( my $log_fh, ">>", "mylog.txt" ) || die "Can't open the log for w
+riting: $!";

my $output = IO::Tee->new( \*STDOUT, $log_fh );

print $output "Starting the script...\n";

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    That should print 'Starting the script...' to both the logfile and the screen. Also, since you now have a couple file handles at your disposal, you can just print to the screen or just print to '$log_fh' at will if you like.
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