SensorBar Helper

Open-source privileged XPC helper for reading macOS SMC sensor data.

This is the helper daemon component of SensorBar, a macOS menu bar system monitor. It runs as a LaunchDaemon with root privileges to access the System Management Controller (SMC) via IOKit, then serves sensor data to the sandboxed SensorBar app over XPC.

What It Does

• Reads hardware sensor data directly from the SMC via IOKit
• Exposes temperature, fan speed, voltage, and power readings
• Communicates with the main SensorBar app via a secure XPC Mach service

Sensors Supported

• Temperature — CPU cores (Intel & Apple Silicon), GPU, memory, SSD, ambient, battery
• Fan Speed — Current RPM, min/max for all fans
• Voltage — CPU, GPU, memory, battery, DC input
• Power — CPU package/cores, GPU, battery, system total

Building

swift build

Requires macOS 13+ and Xcode 15+.

Installation

The helper is normally installed automatically by SensorBar. For manual installation:

1. Build the helper: swift build -c release
2. Copy the binary to /Library/PrivilegedHelperTools/com.ikeybenz.sensorbar.helper
3. Install the LaunchDaemon plist to /Library/LaunchDaemons/com.ikeybenz.sensorbar.helper.plist

Architecture

• main.swift — Entry point; sets up the XPC listener on the Mach service
• SMCReader.swift — Low-level SMC access via IOKit (based on patterns from exelban/stats, MIT License)
• HelperDelegate.swift — XPC delegate and protocol implementation
• SensorBarHelperProtocol.swift — Shared XPC protocol definition

License

MIT