How to use the command 'xbacklight' (with examples)

The xbacklight command is a powerful utility for users running the X Window System, particularly useful in managing the brightness of a laptop or desktop screen. It leverages the RandR extension to adjust and query the backlight settings, making it a convenient tool for those in need of quick adjustments without navigating through menus. By using a few simple commands, you can retrieve and modify the brightness levels of your screen in a flexible and straightforward manner.

Use case 1: Get the current screen brightness as a percentage

Code:

xbacklight

Motivation: Understanding the current brightness level of your screen can be particularly useful if you’re unsure about the existing configuration or if you’re planning to make adjustments. This can be essential in both saving power and protecting your eyes from excessive strain, especially in low-light environments.

Explanation: The command xbacklight without any additional arguments fetches and displays the current brightness level as a percentage. This simplicity is beneficial for users who wish to quickly assess their screen settings without making changes.

Example Output:

75.000000

Here, the output indicates that the screen is currently set to 75% brightness.

Use case 2: Set the screen brightness to 40%

Code:

xbacklight -set 40

Motivation: Reducing the screen brightness to a specific percentage, such as 40%, may be desired when working in a dimly lit environment or when aiming to extend battery life. Setting a precise brightness level allows for a consistent viewing experience and can contribute to energy conservation.

Explanation: The -set option allows you to specify the desired brightness level. By following -set with a numeric value, in this case, 40, xbacklight adjusts the screen’s brightness directly to the given percentage.

Example Output: No direct output is produced by this command, but the screen’s brightness changes visibly to 40%.

Use case 3: Increase current brightness by 25%

Code:

xbacklight -inc 25

Motivation: Increasing the screen brightness when transitioning from a dark room to a brighter environment is critical for screen visibility. By incrementing the brightness by 25%, you can quickly enhance the backlight to better suit your new surroundings without specifying an exact total brightness level.

Explanation: The -inc option, short for “increase,” adds the specified percentage, here 25%, to the current brightness level. This is useful for gradual adjustments rather than setting an absolute brightness level.

Example Output: As with setting brightness, no explicit terminal output is generated, but the screen appears noticeably brighter by 25%.

Use case 4: Decrease current brightness by 75%

Code:

xbacklight -dec 75

Motivation: Lowering the brightness considerably, such as by 75%, can be beneficial if you’re working late at night and want to minimize light pollution in the room. It can also help conserve battery power during extended periods of unplugged use.

Explanation: The -dec option stands for “decrease” and reduces the current brightness level by the given percentage, in this instance, 75%. This provides a quick way to dim the screen significantly without needing to know the existing brightness level.

Example Output: Once again, there is no terminal output, but your screen will appear much dimmer by 75%.

Use case 5: Increase backlight to 100%, over 60 seconds, using 60 steps

Code:

xbacklight -set 100 -time 60000 -steps 60

Motivation: Transitioning screen brightness smoothly is aesthetically pleasing and can be easier on the eyes. By gradually increasing the brightness to its maximum over a minute, you ensure that the change is not jarring, which can be especially useful in presentations or when adjusting to sunlight-filled rooms.

Explanation: Here, the -set 100 component sets the brightness to 100%. The -time 60000 parameter specifies that this adjustment should occur over 60,000 milliseconds, or 60 seconds. The -steps 60 argument breaks down this transition into 60 individual increments, allowing the change to happen progressively.

Example Output: No visible output will appear in the terminal, but the screen will gradually brighten over the course of one minute, reaching full brightness.

Conclusion

The xbacklight command is a versatile and efficient tool for managing screen brightness in Unix-like systems that use the X Window System. Whether you need to fine-tune your monitor’s settings for energy efficiency, visual comfort, or gradual adjustments for presentations, xbacklight offers a range of options to meet your needs with ease.