Bash Gotchas

This kind of shit is why sysadmins drink.

(( )) can return false

Iff the expression in (( blah )) evaluates to <0, the (( )) returns false, so your set -e script will fall on its arse.

pipes into read can return false for no reason

In some old versions of bash (e.g. RHEL6), piping commands into while read -r blah from the left will return false unchecked at the end of the stream, so set -e will make a mockery of you.

Use while read -r blah; do something; done < <(command>) instead.