CIDR to netmask in bash.

cidr-to-netmask.sh

# Return netmask for a given network and CIDR.
cidr_to_netmask() {
    value=$(( 0xffffffff ^ ((1 << (32 - $1)) - 1) ))
    echo "$(( (value >> 24) & 0xff )).$(( (value >> 16) & 0xff )).$(( (value >> 8) & 0xff )).$(( value & 0xff ))"
}

Cool. But why $2 and not $1? :)

@ckuhtz, I copied this from a larger script of mine, just to memoize it here for my future reference, and where there was something else there to do. But that was many years ago, and I don't quite remember. 😄 Fixed now! Thank you!

Awesome! 👏🏻😀 very useful.

@ckuhtz, I am glad you found it useful!