Tag: Awk

There are many occasions when it can be useful to take the IP address of a host and convert that into a decimal number. Create a new file called ip2dec on your system containing the following code

#!/usr/bin/awk -f
BEGIN {
    ip = ARGV[1]
    split(ip, octets, ".")
    for (i = 1; i <= 4; i++) {
        dec += octets[i] * 256 ** (4 - i)
    }
    printf("%i\n", dec)
}

Then make the file executable by running

$ chmod +x ip2dec

This script will take a single IP address as an input parameter and will output the decimal equivalent as shown below

$ ./ip2dec 192.168.1.1
3232235777

The script will convert any IP address from from 0.0.0.0 to 255.255.255.255 to its numeric equivalent which will be within the range 0 to 4294967295.

It is also fairly straight-forward to convert back from a Number to an IP Address. I tend to put these scripts into a folder on my system that is included in my PATH variable, so I can use them whenever needed.

On occasion, it is necessary to convert from a numeric value to an IP address, particularly if that numeric value was created by converting from an IP address. In a previous article, I showed how to Convert an IP Address to a Number, here I will show you how to reverse that process.

Create a new file called dec2ip on your system containing the following code

#!/usr/bin/awk -f
BEGIN {
    dec = ARGV[1]
    for (e = 3; e >= 0; e--) {
        octet = int(dec / (256 ^ e))
        dec -= octet * 256 ^ e
        ip = ip delim octet
        delim = "."
    }
    printf("%s\n", ip)
}

Then make the file executable by running

$ chmod +x dec2ip

This script will take a single numeric value as an input parameter and will output the equivalent IP address as shown below

$ ./dec2ip 3232235777
192.168.1.1

The script will convert any numeric value from 0 to 4294967295 to its IP address equivalent from 0.0.0.0 to 255.255.255.255. Anything outside of that range will produce unexpected results.

I tend to put these scripts into a folder on my system that is included in my PATH variable, so I can use them whenever needed.