    #!/bin/sh

    LED_DIR="/sys/class/leds/RED-LED"
    BRIGHTNESS="$LED_DIR/brightness"
    TRIGGER="$LED_DIR/trigger"

    # ݂̃gKۑi: 'timer', 'heartbeat', 'none' Ȃǁj
    ORIG_TRIGGER="$(cat "$TRIGGER" | sed 's/\[//; s/\]//')"

    cleanup() {
      # IɌ̃gK֖߂
      if [[ -n "$ORIG_TRIGGER" ]]; then
        echo "$ORIG_TRIGGER" > "$TRIGGER" || true
      fi
    }
    trap cleanup EXIT INT TERM

    echo none > "$TRIGGER"

    # 100ms œ_œ_
    while true; do
      echo 1 > "$BRIGHTNESS"  # ON
      sleep 0.1
      echo 0 > "$BRIGHTNESS"  # OFF
      sleep 0.1
    done
