This is a small subroutine to convert a decimal IP address to its binary equivalent. The function takes an IP address and an optional delimter to separate the bytes. I am in the process of writing a small tutorial on the basics of TCP/IP networking and I'm using this function to generate examples. It might also be useful for determining CIDR style netmasks (192.168.10.0/24) such as those used by nmap and Apache allow/deny directives with a little work. 

ip2bin('255.255.255.0', ' ')
returns 
11111111 11111111 11111111 00000000

Update:

Another way to do this is to use the inet_aton function in the Socket module. A perl one liner to produce the same output:

perl -MSocket -e 'printf ("%s %s %s %s", unpack('B8B8B8B8', inet_aton('255.255.255.0')))'

Thanks AgentM for the pointer.

sub ip2bin{
    my ($ip, $delimiter) = @_;
    return     join($delimiter,  map 
        substr(unpack("B32",pack("N",$_)),-8), 
        split(/\./,$ip));
}

[download]

Replies are listed 'Best First'.
Re: Converting decimal IP addresses to binary
by AgentM (Curate) on Jan 30, 2001 at 23:49 UTC
    It should would be nice if you could extend these examples to recognize and manipulate IPv6-level IPs- especially in a tutorial about TCP/IP.
    AgentM Systems nor Nasca Enterprises nor Bone::Easy nor Macperl is responsible for the comments made by AgentM. Remember, you can build any logical system with NOR.
[reply]
      IPv6 is beyond the scope of my tutorial which is for internal staff training, but I don't mind doing IPv6 versions of my conversion functions for PM. Should I add the IPv6 versions to the snippets I've already submitted or should I create new ones? I'm still a bit new here and not sure of monkly etiquette.

      ----
      Coyote

[reply]
        Heck, I'd be more willing to ++ a plus that had more effort put into it (++IPv6). One question though, aren't your functions functionally equivalent to the inet_xxx series combined with an sprintf to return a human-readable string?
        AgentM Systems nor Nasca Enterprises nor Bone::Easy nor Macperl is responsible for the comments made by AgentM. Remember, you can build any logical system with NOR.
[reply]

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