How to read ANSI keyboard sequences in Bash

readkey

readkey() {
    local char
    IFS= \
    read -rs -d '' -N1 key || return $?     # use -n1 on older versions
    while
        case "$key" in
        ('')  key=$'\n' ; break ;;          # compensate for bug
        ( $'\e[M'??? ) break ;;             # mouse report
        ( $'\e' | $'\e[' | $'\e['[?O] | $'\e['*[\;0-9] | $'\e[M'* | $'\eO' ) ;;
        ( [$'\xc0'-\$'xfe'] \
        | [$'\xe0'-\$'xfe'][$'\x80'-$'\xbf'] \
        | [$'\xf0'-\$'xfe']?[$'\x80'-$'\xbf'] \
        | [$'\xf8'-\$'xfe']??[$'\x80'-$'\xbf'] \
        | [$'\xfc'-\$'xfe']???[$'\x80'-$'\xbf'] \
        | [$'\xfe'-\$'xfe']????[$'\x80'-$'\xbf'] ) ;;  # don't stop on incomplete UTF-8 prefix
        (*) break ;;                        # stop on anything else
        esac
        IFS= \
        read -rs -d '' -N1 -t0.1 char       # use -n1 -t1 on older versions
    do
        [[ -z "$char" ]] && char=' '  # compensate for bug
        key="$key$char"
    done
    return 0
}

The "return value" is in $key