Prevent Mac Sleep with Caffeinate

The caffeinate command is a powerful utility for macOS users to prevent their system from entering sleep mode. This is particularly useful for developers who need to run long processes, downloads, or presentations without interruption. By default, macOS has power-saving features that put the system to sleep after a period of inactivity, but caffeinate offers a way to override this behavior.

How to Use Caffeinate

You can use caffeinate in several ways, depending on your needs. Here are some common examples:

Prevent Mac Sleep for a Specific Duration

To prevent your Mac from sleeping for a set amount of time, use the -t flag followed by the duration in seconds. For instance, to keep your Mac awake for 1 hour (3600 seconds):

caffeinate -u -t 3600

The -u flag asserts that the user is active, which is often necessary for the timer to function correctly.

Prevent Mac Sleep Until a Command Completes

A very common and useful application of caffeinate is to keep the system awake while a specific command is running. This ensures that long-running scripts or processes are not interrupted by sleep mode. Use the -s flag for this purpose:

caffeinate -s your_command_here

Replace your_command_here with the actual command you want to execute. The system will remain awake until your_command_here finishes.

Understanding Caffeinate Options

The caffeinate command offers various options to fine-tune its behavior. Some key flags include:

• -d: Prevent the display from sleeping.
• -i: Prevent the system from idle sleeping.
• -m: Prevent the disk from idle sleeping.
• -s: Prevent the system from sleeping when plugged into AC power.
• -u: Assert that the user is active.
• -t seconds: Specify a timeout in seconds.

External Resources

• caffeinate man page
• Preventing Mac Sleep on Stack Exchange