source: vendor/bash/3.1-p17/examples/functions/notify.bash

trap _notify CHLD
NOTIFY_ALL=false
unset NOTIFY_LIST
unalias false

false()
{
        return 1
}

_notify ()
{
        local i j
        local newlist=

        if $NOTIFY_ALL
        then
                return          # let bash take care of this itself
        elif [ -z "$NOTIFY_LIST" ]; then
                return
        else
                set -- $NOTIFY_LIST
                for i in "$@"
                do
                        j=$(jobs -n %$i)
                        if [ -n "$j" ]; then
                                echo "$j"
                                jobs -n %$i >/dev/null
                        else
                                newlist="newlist $i"
                        fi
                done
                NOTIFY_LIST="$newlist"
        fi
}

notify ()
{
        local i j

        if [ $# -eq 0 ]; then
                NOTIFY_ALL=:
                set -b
                return
        else
                for i in "$@"
                do
                        # turn a valid job spec into a job number
                        j=$(jobs $i)
                        case "$j" in
                        [*)     j=${j%%]*}
                                j=${j#[}
                                NOTIFY_LIST="$NOTIFY_LIST $j"
                                ;;
                        esac
                done
        fi
}