Removing leading zeros before passing a shell variable to another command

Question

It turns out that iptables doesn\'t handle leading zeros too well. As $machinenumber that is used has to have a leading zero in it for other purposes, the idea

Answer 1

I would say you are very close. I do not see a requirement stated for bash, but your nonzero logic is flawed.

nonzero=`echo $machinenumber + 0 | bc`
iptables -t nat -I POSTROUTING -s 10.$machinetype.$nozero.0/24 -j MASQUERADE

Adding 0 is a common method for changing a string number into a non-padded integer. bc is a basic calculator. I use this method for removing space and zero padding from numbers all the time.

While I am not expert in iptables syntax, I am pretty sure the parenthesis are not necessary. Since I already have non-word characters bordering both variables, I do not need special enclosures around them. Word characters are;

[a-zA-z0-9_]

Using this solution, you do not lose zero as a potential value, and should be portable across all shells.