iSMC

About

iSMC is a macOS command-line tool for querying the Apple System Management Controller (SMC). It reads a broad set of well-known SMC keys, determines their type and value, and classifies the results into temperature, power, current, voltage, fan, and battery readings. Each key is accompanied by a human-readable description.

In addition to standard SMC support for Intel Mac hardware, iSMC supports Apple Silicon: the full M1–M5 line (including Pro/Max/Ultra variants where they exist) plus the A18 Pro used by the MacBook Neo (Mac17,5). On these models, temperature, voltage, and current sensors are read through a HID sensor hub; power readings still come through the SMC path.

Installation

iSMC runs on macOS only.

Homebrew

You can install iSMC using Homebrew by adding the homebrew-tap tap and installing the ismc package:

brew tap dkorunic/tap
brew install ismc

Manual

Download the appropriate iSMC binary for your platform from the releases page and install it manually.

Using go install

You can also install iSMC using the go install command:

CGO_ENABLED=1 go install github.com/dkorunic/iSMC@latest

Usage

Apple SMC CLI tool that can decode and display temperature, fans, battery, power, voltage and current
information for various hardware in your Apple Mac hardware.

Usage:
  iSMC [flags]
  iSMC [command]

Available Commands:
  all         Display all known sensors, fans and battery status
  batt        Display battery status
  completion  Generate the autocompletion script for the specified shell
  curr        Display current sensors
  fans        Display fans status
  guess       Map SMC temperature sensors to CPU cores by thermal correlation
  help        Help about any command
  hw          Display hardware information
  power       Display power sensors
  raw         Display all raw SMC keys and their byte values
  temp        Display temperature sensors
  version     Print the version number of iSMC
  volt        Display voltage sensors

Flags:
  -h, --help            help for iSMC
  -o, --output string   Output format (ascii, table, json, influx) (default "table")

Use "iSMC [command] --help" for more information about a command.

Each command also accepts short and long aliases: bat/batt/battery, cur/curr/current, fan/fans, hw/hardware/info, pow/power, tmp/temp/temperature, vol/volt/voltage, all/everything/*.

Output formats

Format	Description
table	Coloured terminal table (default)
ascii	Plain ASCII table
json	JSON
influx	InfluxDB line protocol

Architecture

iSMC reads sensors through two hardware paths and unifies them at the output layer:

• SMC path — works on Intel/PPC Macs, and on Apple Silicon for power readings. Built on gosmc, a CGo wrapper around Apple's IOKit SMC interface.
• HID path — Apple Silicon only. Reads temperature, voltage, and current from the HID sensor hub via CGo into IOKit HID services.

internal/cmd/            Cobra subcommands
  └─ internal/output/    Output interface — selects table | ascii | json | influx
       ├─ smc.Get*()     named SMC keys (Intel/PPC + Apple Silicon power)
       │    └─ gosmc      CGo → IOKit SMC
       └─ hid.Get*()     HID sensor hub (Apple Silicon temp / volt / curr)
            └─ C/IOKit    CGo → IOKit HID services

Package layout

Path	Visibility	Purpose
gosmc/	public (separate Go module)	Low-level IOKit SMC bindings via CGo
smc/	public	Named-key SMC sensor reader, built on gosmc
hid/	public	Apple Silicon HID sensor reader (embedded C)
internal/cmd/	internal	Cobra subcommand wiring
internal/output/	internal	Output interface + four backend formatters
internal/platform/	internal	CPU family / SKU detection used by smc
internal/reports/	internal	Diagnostic report bundler
internal/stress/	internal	CPU affinity / QoS helpers for the guess workload

The repo is two Go modules: the root github.com/dkorunic/iSMC and the nested github.com/dkorunic/iSMC/gosmc (replaced locally via go.mod). internal/ packages are compiler-enforced private to this module; the three public packages are the intended library surface.

smc/sensors.go is code-generated from src/{temp,fans,power,voltage,current}.txt by smc/gen-sensors.sh. Regenerate via task generate after editing the .txt files — do not edit sensors.go by hand.

All source files carry a //go:build darwin constraint; the project is macOS-only by construction and will not build or test on other platforms regardless of CGO_ENABLED.

Related work

This tool was inspired by several Apple SMC-related projects:

• SMCKit — Apple SMC library and tool in Swift: github.com/beltex/SMCKit
• libsmc — SMC API in pure C: github.com/beltex/libsmc
• iStats — Ruby gem for Mac stats: github.com/Chris911/iStats
• smcFanControl — Fan control tool in Objective-C, includes smc-command for raw SMC key queries: github.com/hholtmann/smcFanControl
• FakeSMC — Hackintosh kext: github.com/RehabMan/OS-X-FakeSMC-kozlek
• VirtualSMC — Hackintosh kext: github.com/acidanthera/VirtualSMC
• osx-cpu-temp — CPU temperature display in pure C: github.com/lavoiesl/osx-cpu-temp
• applesmc.c — Linux kernel Apple SMC driver: github.com/torvalds/linux
• gosmc — Low-level Go SMC bindings: github.com/panotza/gosmc
• sensors — Koan-Sin Tan's M1 IOKit demo: github.com/freedomtan/sensors
• Stats — Serhiy Mytrovtsiy's macOS Stats app: github.com/exelban/stats

Todo

Planned features:

• fetch and decode SMC key descriptions from the SMC itself,
• generate and probe random SMC keys,
• persist discovered SMC keys to a configuration file.

Bugs, feature requests, etc.

Please open an issue or submit a pull request.

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