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

#!/bin/perl

use strict;
use warnings;
use diagnostics;
use Term::ANSIColor;
use JSON;
use Data::Dumper;

open(my $fh, '<', '/home/david/dev/linux.json');
my $json_text = <$fh>;
my $test_scalar = decode_json($json_text);

my $max = 10;
my $count = 0;
my $quit = 0;

sub reddit {
        while ($count <= $max) {
                print colored ['red'], "-> $test_scalar->{data}{childr
+en}[$count]{data}{title}\n";
                print colored ['yellow'], "$test_scalar->{data}{childr
+en}[$count]{data}{url}\n";
                $count++;
        }
}

reddit();

my $wait = <STDIN>;
chomp($wait);

if ($wait eq '\cR') {
        reddit();
}

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I have a problem with executing a subroutine when an IF-statement evaluates to true. What am I doing wrong? The only thing that happends when I press control+r is that the script exits. The code isn't pretty, any pointers on how to make this code prettier are welcome! Regards, David

Replies are listed 'Best First'.
Re: Executing a subroutine in an IF
by morgon (Priest) on Jun 16, 2012 at 00:12 UTC
    First: '\cR' is NOT control-R - it is a three character string.

    You want double-quotes: "\cR"

    And you cannot read a control-r just like that. You need to put your terminal into raw mode which you can do via Term::ReadKey: 

    use strict;

use Term::ReadKey;
ReadMode 4;           # raw mode
my $key = ReadKey(0);   # read a character
ReadMode 0;           # back to normal mode

if($key eq "\cR") {
 # do whatever you want to do
 print "got ctrl-R!\n";
}

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[reply]
[d/l]
[select]
      Hi morgon, Thank you for the answer. Reading the key works just fine now, but the sub still won't execute. I feel as if this should work .. read the key, if it's ctrl-r then execute the subroutine. Am I missing something crucial here? Regards, David
[reply]

        I feel kind of foolish now, I forgot to reset the $count scalar to 0 before calling the subroutine again. It works as intended now. :-)

        #!/bin/perl

use strict;
use warnings;
use diagnostics;
use Term::ANSIColor;
use Term::ReadKey;
use JSON;

open(my $fh, '<', '/home/david/dev/linux.json');
my $json_text = <$fh>;
my $test_scalar = decode_json($json_text);

my $max = 10;
my $count = 0;

sub reddit {
        while ($count <= $max) {
                print colored ['red'], "-> $test_scalar->{data}{childr
+en}[$count]{data}{title}\n";
                print colored ['yellow'], "$test_scalar->{data}{childr
+en}[$count]{data}{url}\n";
                $count++;
        }
}

reddit();

ReadMode 4;
my $wait = ReadKey(0);
ReadMode 0;

if ($wait eq "\cR") {
        $count = 0;
        reddit();
}

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