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

Hello Monks,

I have a piece of code which checks if a string is an IP Address or not and prints a 1 if the string is a valid IP and 0 otherwise. 

#!/usr/bin/perl

use strict;
use warnings;

main();
exit;

###############################################

sub main {

    my $ip = qq{127.0.0.1};
    print "IP Validity Status:". validate_ip_addr($ip),$/;
}

sub validate_ip_addr {

    my ($addr_to_check) = shift;
    return ( $addr_to_check =~ m/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/
+ );
}

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If the ip is valid, this piece of code prints: 
IP Validity Status:1

[download]
However, if the IP is invalid, what I see is: 
IP Validity Status:

[download]
How do I make it print: 
IP Validity Status:0

[download]
?

TIA,

Replies are listed 'Best First'.
Re: printing true false values
by McDarren (Abbot) on Dec 30, 2007 at 16:06 UTC
    You have an answer to your immediate problem, however....

    Matching a valid IP address is not quite as simple as it might seem at first. For example, your regex would match 999.999.999.999, which is certainly not a valid IP.

    Rather than trying to roll your own, you might want to take a look at Data::Validate::IP - all the tough work has been done for you.

    Cheers,
    Darren :)

[reply]
      Thanks a lot Darren. This is definitely the best solution.
[reply]
Re: printing true false values
by jasonk (Parson) on Dec 30, 2007 at 15:51 UTC 
    print "IP Validity Status:". ( validate_ip_addr( $ip ) ? 1 : 0 )."\n";

    [download]
    We're not surrounded, we're in a target-rich environment!
[reply]
[d/l]
      Thanks Jason and FunkyMonk, for the quick response. I did think of doing something similar: using the if else. However, by the definition of truth values in perl, 0 represents false and anything else represents true. So, if a boolean expression evaluates to true, it will return a 1 and if it evaluates to false, shouldn't it return a 0?
[reply]
        perlsyn.pod says:
        Truth and Falsehood
        The number 0, the strings ’0’ and ’’, the empty list "()", and "undef" are all false in a boolean context. All other values are true. Negation of a true value by "!" or "not" returns a special false value. When evaluated as a string it is treated as ’’, but as a number, it is treated as 0.
[reply]
        What values are considered true and false is not the same thing as what an expression evaluates to. Many Perl operators that evaluate to a boolean evaluate to 1 when true and '' (the empty string) when false.
[reply]
[d/l]
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[d/l]
        you could force numerical context
[reply]
Re: printing true false values
by jwkrahn (Abbot) on Dec 30, 2007 at 16:05 UTC 
    use Socket;

my $ip = '127.0.0.1';

print 'IP Validity Status:', inet_aton( $ip ) ? 1 : 0, "\n";

    [download]
[reply]
[d/l]
Re: printing true false values
by FunkyMonk (Bishop) on Dec 30, 2007 at 15:52 UTC
    Change your return to 
    return ( $addr_to_check =~ m/(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/ )
  ? 1 : 0;

    [download]

[reply]
[d/l]
[select]
Re: printing true false values
by ysth (Canon) on Dec 30, 2007 at 23:49 UTC
[reply]
[d/l]

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