How can I access thermal sensors on Mac using CLI?

Question

Level 1

95 points

How can I access thermal sensors on Mac using CLI?

I have a Mac I used to log and monitor thermal sensors. This includes an external USB sensor, and a few of the internal sensors in the Mac.

These are both older intel Macs. I recently upgraded from a 2009 running high sierra, to one a little newer running Catalina. Formerly, to access all of the thermal sensors, I used a program called Hardware Monitor. It was a GUI program but it included a CLI program you could use to poll the sensors.

However that software is abandoned and will not run on Catalina. So now I'm searching for a replacement. I'm not looking for the overall thermal pressure of the machine(aka powermetrics isn't the solution, unless it has features I'm not seeing). I'm looking for raw temperature numbers for all of the internal thermal sensors. Something I can easily grab periodically via my own running script. It hits the internal sensors, then the USB sensors, then loads it all into an sql database.

^ here is the Sensor Overview window from the program Hardware Monitor, running on an older Mac. This is the data I'm trying to access via command line.

[Re-Titled by Moderator]

Earlier Mac models

Posted on May 7, 2025 02:41 AM

Reply

Answer 1

g_wolfman

Level 4

3,454 points

May 7, 2025 01:35 PM in response to Camelot

There are lots of such tools. System Monitor is another: https://apps.apple.com/ca/app/system-monitor/id423368786?mt=12, for which the developer has an add-on tool that will access the sensor data, including for Apple Silicon.

Reply

Answer 2

l008com Author

Level 1

95 points

May 11, 2025 01:09 AM in response to l008com

I have found what appears to be the perfect solution to my dilemma, a program called iSMC:

https://github.com/dkorunic/iSMC

Reply

Answer 3

Camelot

Level 9

57,873 points

May 7, 2025 10:39 AM in response to l008com

A LOT of this depends on the system you're running.

Apple Silicon chips (M1/M2/M3/M4) don't report CPU temperatures in the same way that Intel chips do, due to a completely different thinking behind chip performance, thermal throttling, etc.

As such, much of what you're looking for just isn't available (or relevant) for Apple Silicon-based devices.

Apple Silicon only reports temperature in buckets of 'Nominal', 'Fair', 'Serious', or 'Critical', with no direct degrees C/F readout.

The best you can get right now is via either systemstats or powermetrics and it sounds like you're already familiar with those.

This doesn't directly explain why non-CPU temperature metrics aren't available either, but they seem to be absent, too.

Reply

Answer 4

l008com Author

Level 1

95 points

May 7, 2025 11:51 AM in response to Camelot

The new machine is a 2010 iMac running Catalina. It definitely has the full array of thermal sensors. If I install an older OS on it, I can run my old Hardware Monitor app and see them all. So the sensors are all there. I just need a way to access them.

Reply

Answer 5

l008com Author

Level 1

95 points

May 7, 2025 12:16 PM in response to Camelot

Well its good to know that those thermal sensors are still there if i ever upgrade to a more modern machine. But that will be a while, this project always runs ~10 year old Macs.

But still, having the temps in a menu is no use to me, I need to be able to get those value into my script and ultimately into my database.

Reply

Answer 6

Camelot

Level 9

57,873 points

May 7, 2025 01:18 PM in response to l008com

I wasn't suggesting that was a solution since you wanted a command-line approach... just saying that someone had managed to work out it.

Digging deeper I did come across an FOSS project stats which does something similar to iStats Menu. Part of this project installs a helper tool smc which does the heavy lifting of extracting the stats from the system. It's not pretty, though, since it's designed to be used within the Stats app, but it does appear to support getting temperatures from the command line:

% smc list -t
[INFO]: found 375 keys

[TAOL]     25.375
[TB0T]     26.599990844726562
[TB1T]     26.199996948242188
[TB2T]     26.599990844726562
[TCDX]     39.25374984741211
[TCHP]     33.50730895996094
...

it looks like there's a selector (TAOL, TB0T, TB1T, etc.) that identifies the sensor along with its value. The sensor codes are likely to be universal, and specific to the machine you're running on, so you'll need to work out which of the 375 codes are relevant for your machine.

If you're a developer, you may also be able to look through the code and extract the specifics for your use case. I haven't looked into that yet.

Reply