How do you you collect the value of a variable with wget in perl?

Question

I am looking to collect the value of <UB> using wget: This the output of my wget

<FPT>0</FPT> <UB>13.5</UB>

And I am looking to gather the value 13.5(that changes) this is what I have so far:

##session wget
my $url= 'wget http://link';
my $html_page = system "wget -S -O - $url";
if($debug){printf "This is a value : $html_page\n";}


#we collect the battery state of the group
use strict;
open (UB, $url);
while (my $volt_batt = <UB>)
{
        if($volt_batt < 13){
                $retour = $ERRORS{'CRITICAL'};
                $output = "CRITICAL - Battery Volt too low: $volt_batt V (<13 V) | batt_volt=$volt_batt\n";
        }
        else{
        if ($volt_batt >= 13){
                $output ="OK, Battery Volt: $volt_batt V (>=13V) | batt_volt=$volt_batt\n";

        }
    }
}

system "$output";
exit $retour; 

Answer 1

This doesn't do what you want:

my $html_page = system "wget -S -O - $url";

You want to use readpipe (aka qx`...` aka `` ).

my $html_page = `wget -S -O - $url`;

Except the above suffers from a code injection bug. Fixed:

use Shell::Quote qw( shell_quote );

my $cmd = shell_quote( "wget", "-S", "-O", "-", $url );

my $html_page = `$cmd`;

You could also avoid the shell entirely by using the following:

my @cmd = ( "wget", "-S", "-O", "-", $url );

my $html_page = do {
   open my $pipe, "-|", @cmd;
   local $/;
   <$pipe>
};

[There are numerous other errors.]