err

#! .desc:
# Print formatted text to stderr
#! .params:
# <$1> - color(
#     '-'  - none
#     '-bk' - black
#     '-r' - red
#     '-g' - green
#     '-y' - yellow
#     '-be' - blue
#     '-m' - magenta
#     '-c' - cyan
#     '-w' - white
#     .
# )
# <$2> - format(
#     '-' - raw
#     '--' - raw; no <newline>
#     '-date' - `date` %H%M%S
#     '-date-' - `date` %H%M%S; no <newline>
#     .
# )
# <"$3">+ - text
#! .uses.var:
# [NO_COLOR] $ - environment variable;
#                disables colored output
#! .rc:
# (0) success
# (255) bad input
#! .caveats:
# > `ARG_MAX`.
# > `INT_MAX`.
#.
err() {
    # Check if color codes should be used.
    if [ "$NO_COLOR" ]; then
        _reset=
        _color=
    else
        _reset='\033[0m'

        case $1 in
            '-') _color=; _reset= ;;
            '-bk') _color='\033[1;30m' ;;
            '-r') _color='\033[1;31m' ;;
            '-g') _color='\033[1;32m' ;;
            '-y') _color='\033[1;33m' ;;
            '-be') _color='\033[1;34m' ;;
            '-m') _color='\033[1;35m' ;;
            '-c') _color='\033[1;36m' ;;
            '-w') _color='\033[1;37m' ;;
            *) return 255 ;;
        esac
    fi

    _format="$2"; shift 2

    case "$_format" in
        '-')
            printf "%b%s%b\n" "$_color" "$*" "$_reset" >&2
        ;;
        '--')
            printf "%b%s%b" "$_color" "$*" "$_reset" >&2
        ;;
        '-date')
            printf "%b[%s] =>>: %s%b\n" "$_color" "$(date '+%H:%M:%S')" "$*" \
                "$_reset" >&2
        ;;
        '-date-')
            printf "%b[%s] =>>: %s%b" "$_color" "$(date '+%H:%M:%S')" "$*" \
                "$_reset" >&2
        ;;
        *)
            return 255
        ;;
    esac

    return 0
}