multiple bash traps for the same signal

Question

When I use the trap command in bash, the previous trap for the given signal is replaced.

Is there a way of making more than one trap<

Answer 1

Simple ways to do it

1. If all the signal handling functions are know at the same time, then the following is sufficient (has said by Jonathan):

trap 'handler1;handler2;handler3' EXIT

2. Else, if there is existing handler(s) that should stay, then new handlers can easily be added like this:

trap "$( trap -p EXIT | cut -f2 -d \' );newHandler" EXIT

3. If you don't know if there is existing handlers but want to keep them in this case, do the following:

 handlers="$( trap -p EXIT | cut -f2 -d \' )"
 trap "${handlers}${handlers:+;}newHandler" EXIT

4. It can be factorized in a function like that:

trap-add() {
    local sig="${2:?Signal required}"
    hdls="$( trap -p ${sig} | cut -f2 -d \' )";
    trap "${hdls}${hdls:+;}${1:?Handler required}" "${sig}"
}

export -f trap-add

Usage:

trap-add 'echo "Bye bye"' EXIT
trap-add 'echo "See you next time"' EXIT

Remark : This works only has long as the handlers are function names, or simple instructions that did not contains any simple cote (simple cotes conflicts with cut -f2 -d \').