Display key code

keycode.sh

#!/bin/sh
set -euf

stty=$(stty -g)
trap 'stty "$stty"' EXIT

stty -echo -icanon

tpid=""
while :; do
    key=$(dd bs=1 count=1 2>/dev/null | od -An -a)
    set -- $key && key=$1
    hex=$(printf "%s" "$key" | od -An -tx1)
    set -- $hex && hex=$1
    case $hex in
        [a-f]?) printf "%s " "$hex" ;;
        *) printf "%s " "$key" ;;
    esac
    [ "$tpid" ] && { kill "$tpid" 2>/dev/null ||:; }
    ( trap exit TERM; sleep 0.1; echo ) & tpid=$!
done