
___x_cmd_rat_(){
    x_=
    local IFS=
    local arg; local line; for arg in "$@"; do
        [ -f "$arg" ] || {
            x:error "Unexisted file=${arg}"
            return 64
        }

        while IFS= read -r line; do
            x_="${x_}${line}
"
        done <"$arg"
    done
}

