I was going to say “it always seems to work for me” then I saw “… actually works in Bash and Zsh, because …”.

Another Bash-ism I need to be careful not to use when trying to be portable.

It is worth noting that on a lot of systems /bin/sh isn't bash (or zsh) so if you want to rely on Bashisms (or just can't be bothered looking for them) be specific and use “#!/bin/bash” for you hashbang. On Debian and similar it is usually dash for instance.