in reply to converting user friendly regex to perl friendly

Generally speaking, it's better to match any number, then make sure it's in range.

# Supports ranges in any number of bytes.

sub parse_ip_mask {
   my ($ip_mask) = @_;
   my $checks = '';
   my $check_num = 0;
   my $ip_re = join('\\.', map {
      if (/\[(\d+)-(\d+)\]/) {
         $check_num++;
         $checks .= " && \$$check_num >= $1";
         $checks .= " && \$$check_num <= $2";
         '(\\d+)'
      } else {
         $_
      }
   } split(/\./, $ip_mask));
   return eval "sub { (\$_[0] || \$_) =~ /^$ip_re\$/$checks }";
}

my $ip_check = parse_ip_mask('131.202.1.[3-4]');

foreach (qw(
   131.202.1.2
   131.202.1.3
   131.202.1.4
   132.202.1.4
)) {
   print(&$ip_check()   # Uses $_ if no arguments are specified.
      ? "$_ matches.$/"
      : "$_ doesn't match.$/"
   );
}

__END__
output
======
131.202.1.2 doesn't match.
131.202.1.3 matches.
131.202.1.4 matches.
132.202.1.4 doesn't match.

[download]

It's possible to do this without eval. Give me a few minutes.

Replies are listed 'Best First'.
Re^2: converting user friendly regex to perl friendly
by ikegami (Patriarch) on Oct 15, 2004 at 18:25 UTC

    A version without eval:

    # Supports ranges in any number of bytes.

sub parse_ip_mask {
   my ($ip_mask) = @_;
   my @checks;
   foreach (split(/\./, $ip_mask)) {
      if (/\[(\d+)-(\d+)\]/) {
         push(@checks, [ 0+$1, 0+$2 ]);
      } else {
         push(@checks, [ 0+$_, 0+$_ ]);
      }
   }
   return \@checks;
}

sub ip_check {
   my ($ip, $checks) = @_;
   my @ip = split(/\./, $ip);
   my $i;
   for ($i=0; $i<4; $i++) {
      return undef if ($ip[$i] < $checks->[$i][0]);
      return undef if ($ip[$i] > $checks->[$i][1]);
   }
   return 1;
}

    [download]

    Example usage #1, check if an IP is in range:

    my $ip_mask = parse_ip_mask('131.202.1.[3-4]');

foreach (qw(
   131.202.1.2
   131.202.1.3
   131.202.1.4
   132.202.1.4
)) {
   print(ip_check($_, $ip_mask)
      ? "$_ matches.$/"
      : "$_ doesn't match.$/"
   );
}

__END__
output
======
131.202.1.2 doesn't match.
131.202.1.3 matches.
131.202.1.4 matches.
132.202.1.4 doesn't match.

    [download]

    Example usage #2, finding matching IPs in a line:

    my $ip_mask = parse_ip_mask('131.202.1.[3-4]');

foreach (
   'Connection established to 131.202.1.2',
   'Connection established to 131.202.1.3',
   'Connection established to 131.202.1.4',
   'Connection established to 132.202.1.4',
) {
   my ($ip) = /(\d+\.\d+\.\d+\.\d+)/;
   print("Found matching ip $ip.$/") if (ip_check($ip, $ip_mask));
}

__END__
output
======
Found matching ip 131.202.1.3.
Found matching ip 131.202.1.4.

    [download]
[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom