Sorry, but 255 and 0 are both valid values for octets. Not that you aren't the first person to make that mistake. Part of the installation process for WinNT doesn't allow 0 octets, which caused us interesting problems. For example, 11.0.255.1 is a perfectly valid IP address. Now you could play lots of games with determining which values are valid for the first octet and/or require that the netmask be passed in and use that to do a proper check... But I don't think such is at all worth it.

I think you misunderstood me (and read my flawed code for help), because what I meant was that 0 and 255 are *NOT* valid values for a *host* in the last octet, but you're right, they're valid anywhere else (except of course, a 0 in the first octet unless you're using all-zeros broadcast, which is non-standard by modern convention, or a 255 in the first octet, which is valid only for broadcast addresses). But that's pedantic.

If you want to do a complete test, the NetAddr::IP module from CPAN (or just use the trick of trying to open a socket with the address and see if it works).

But I did make a mistake; the regexp I wrote does needs to account for 0's in the last octet, provided that the last octet does not contain *only* zeros. So a more correct version would be this, if you wanted to ONLY verify *HOST* addresses and not broadcasts or subnets (please note: the regexp below does not prohibit '255' values in the first or last octet, which are technically invalid for *host* addresses):



unless ($get
        && $get =~ /^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[1-9][0-9]{0,
+2}$/
        && !grep { $_ < 0 || $_ > 255 } split(/\./, $get) )
                { print "BAFFLING: invalid target specified\n"; exit(-
+1);}
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Signature void where prohibited by law.

Actually, what is not allowed for hosts is to have the "host" half of the address (based on the netmask) be all 0 bits or all 1 bits. That still allows for the last octet to be 0 (though not for standard Class C IP addresses, which are the most common for most people).

So I still think trying to disallow such is a mistake.

        - tye (but my friends call me "Tye")