SMCKit

An Apple System Management Controller (SMC) library & command line tool in Swift for Intel based Macs. The library works by talking to the AppleSMC.kext (kernel extension), the private driver for the SMC. Read temperature sensors, get and set fan speed (RPM), and more.

• For an example usage of this library, see dshb, a macOS system monitor in Swift
• For other system related statistics in Swift for macOS, see SystemKit

System Management Controller

"The System Management Controller (SMC) is an internal subsystem introduced by Apple Inc. with the introduction of their new Intel processor based machines in 2006. It takes over the functions of the SMU. The SMC manages thermal and power conditions to optimize the power and airflow while keeping audible noise to a minimum. Power consumption and temperature are monitored by the operating system, which communicates the necessary adjustments back to the SMC. The SMC makes the changes, slowing down or speeding up fans as necessary." -via Wikipedia

For more see:

• System Management Controller
• System Management Unit
• Power Management Unit

Requirements

• Xcode 9.0 (Swift 4.0)
• macOS 10.12 Sierra and above for development (due to Xcode)
• OS X 10.9 Mavericks and above for use (due to Swift)

Clone

Make sure to use the recursive option on clone to initialize all submodules.

git clone --recursive https://github.com/beltex/SMCKit

Incase you have already cloned the repository, run the following inside the project directory.

git submodule update --init

SMCKitTool

A macOS command line tool for interfacing with the SMC using SMCKit. The CommandLine library is used for the CLI and ronn for generating the manual page.

Install

This will build SMCKitTool (smckit(1)) from source and place the binary and manual page in your path.

make install

Example

$ smckit
-- Temperature --
AMBIENT_AIR_0           34.0°C
CPU_0_DIE               48.0°C
CPU_0_PROXIMITY         39.0°C
ENCLOSURE_BASE_0        29.0°C
ENCLOSURE_BASE_1        29.0°C
ENCLOSURE_BASE_2        28.0°C
HEATSINK_1              34.0°C
MEM_SLOTS_PROXIMITY     36.0°C
PALM_REST               27.0°C
-- Fan --
[id 0] Right Side
    Min:      1299 RPM
    Max:      6199 RPM
    Current:  1292 RPM
-- Power --
AC Present:       true
Battery Powered:  false
Charging:         false
Battery Ok:       true
Battery Count:    1
-- Misc --
Disc in ODD:      false

Library Usage Notes

• The use of this library will almost certainly not be allowed in the Mac App Store as it is essentially using a private API
• If you are creating a macOS command line tool, you cannot use SMCKit as a library as Swift does not currently support static libraries. In such a case, the SMC.swift file must simply be included in your project as another source file. See SwiftInFlux/Runtime Dynamic Libraries for more information and both SMCKitTool & dshb as examples of such a case.

References

There are many projects that interface with the SMC for one purpose or another. Credit is most certainly due to them for the reference. Such projects as:

• iStat Pro
• osx-cpu-temp
• PowerManagement
• powermetrics(1)
• smcFanControl

Handy I/O Kit references:

• iOS Hacker's Handbook
• Mac OS X and iOS Internals: To the Apple's Core
• OS X and iOS Kernel Programming

License

This project is under the MIT License.

Fun

While the SMC driver is closed source, the call strucutre and definition of certain structs needed to interact with it (see SMCParamStruct) happened to appear in the open source Apple PowerManagement project at around version 211, and soon after disappeared. They can be seen in the PrivateLib.c file under pmconfigd. In the very same source file, the following snippet can be found:

// And simply AppleSMC with kCFBooleanTrue to let them know time is changed.
// We don't pass any information down.
IORegistryEntrySetCFProperty( _smc,
                    CFSTR("TheTimesAreAChangin"),
                    kCFBooleanTrue);

Almost certainly a reference to Bob Dylan's The Times They Are a-Changin' :)