noSleep

noSleep is a small macOS utility that keeps a Mac awake when the lid is closed and AC power is connected.

The current build separates the human-facing CLI from the long-running daemon:

• noSleep: Swift CLI for install-time and user commands.
• noSleepDaemon: minimal C daemon run by launchd.

This keeps the always-running process small while preserving the original user commands and behavior.

Behavior

State	Result
AC power connected and lid closed	Prevent system sleep
AC power connected and lid open	Allow normal macOS behavior
Battery power	Allow normal macOS behavior

Closing the lid posts a "Sleep prevention active" notification. Opening the lid or switching out of the protected state posts a restore notification and plays a single restore sound. The lid-close sound is intentionally suppressed because macOS can defer audio during clamshell transitions and replay it on lid-open.

Requirements

• macOS
• Xcode Command Line Tools
• swiftc
• clang
• launchctl

Install Xcode Command Line Tools if needed:

xcode-select --install

Install

./install.sh
noSleep start

The installer:

• builds the Swift CLI as ~/bin/noSleep
• builds the minimal daemon as ~/bin/noSleepDaemon
• creates ~/Library/Application Support/noSleep
• installs ~/Library/LaunchAgents/com.noSleep.daemon.plist
• points launchd stdout and stderr at /dev/null
• validates the generated plist with plutil -lint

The installer intentionally leaves the local ./noSleep build artifact in the repository directory.

Commands

noSleep              # Show help
noSleep status       # Show power, lid, daemon, and launchd state
noSleep start        # Start the daemon via launchd
noSleep stop         # Stop the daemon but keep installed files
noSleep restart      # Restart the daemon via launchd
noSleep doctor       # Run read-only diagnostics
noSleep daemon       # Exec the installed daemon, or run Swift fallback
noSleep uninstall    # Stop and remove installed files
noSleep --version    # Show version
noSleep --help       # Show help

Runtime Footprint

The daemon is event-driven. It does not poll. It listens for IOKit clamshell and power-source notifications, then creates or releases one PreventSystemSleep assertion.

Expected idle shape after startup:

• one daemon thread
• no stdout/stderr log files
• one lock-file descriptor
• no polling loop
• no permanent notification worker thread

Typical open-file view:

/
~/bin/noSleepDaemon
/usr/lib/dyld
~/Library/Application Support/noSleep/noSleep.lock

Activity Monitor and lsof also report mapped runtime objects such as the executable and dyld; those are not files created by noSleep.

macOS may still report page faults or page-ins for first access to executable or shared library pages. noSleep cannot force those counters to zero, but the daemon is structured to avoid idle churn.

Installed Files

Current install:

~/bin/noSleep
~/bin/noSleepDaemon
~/Library/LaunchAgents/com.noSleep.daemon.plist
~/Library/Application Support/noSleep/noSleep.lock

Legacy cleanup support:

/tmp/noSleep.lock
/tmp/noSleep.log
/tmp/noSleep.err
~/Library/Logs/noSleep

noSleep uninstall removes the installed binaries, launchd plist, lock file, state directory, and legacy cleanup paths when they are owned by the current user and safe to remove.

Design Notes

The original Swift-only daemon was simple and readable, but the long-running process also carried CLI helpers, Foundation process-spawning utilities, and notification code. The current design keeps that code in the CLI path and runs a smaller dedicated daemon under launchd.

Security and correctness hardening includes:

• state directory under ~/Library/Application Support/noSleep
• lock file created with O_NOFOLLOW, O_CLOEXEC, and mode 0600
• lock-file owner, type, and hardlink validation
• full-write PID update with fsync
• PID validation through proc_pidpath
• direct Process usage in Swift instead of shell strings
• direct posix_spawn in the daemon for notifications and sounds
• strict C compiler warnings promoted to errors
• clang --analyze clean daemon source

Troubleshooting

Check current state:

noSleep status
noSleep doctor

Restart the daemon:

noSleep restart

Fully remove the install:

noSleep uninstall

If the daemon is running but the current shell cannot find noSleep, make sure ~/bin is in your PATH.

License

GPLv3. See LICENSE.