I implemented defer as a bash loadable builtin.It is a wrapper over the trap builtin that chains handlers on signals instead of replacing them (LIFO order):https://github.com/leagris/bash-loadable-defer
Is this better than
trap_append () { trap "$(printf "%s\n$1" "$(trap -P "$2")")" "$2"; }
trap_prepend () { trap "$(printf "$1\n%s" "$(trap -P "$2")")" "$2"; }
?
