Calling sysctl from python via ctypes

python_sysctl.py

from ctypes import CDLL, c_uint, byref, create_string_buffer
from ctypes.util import find_library
libc = CDLL(find_library("c"))

def sysctl(name, isString=True):
    size = c_uint(0)
    # Find out how big our buffer will be
    libc.sysctlbyname(name, None, byref(size), None, 0)
    # Make the buffer
    buf = create_string_buffer(size.value)
    # Re-run, but provide the buffer
    libc.sysctlbyname(name, buf, byref(size), None, 0)
    if isString:
        return buf.value
    else:
        return buf.raw

I am attempting to use this on a MacBook Pro 13-inch, M1, 2020 running macOS Monterey 12.5. I am using Python 3.10.5 downloaded from the official Python.org site.

I am trying to capture the equivalent of running "sysctl hw.model" from Terminal. When I run that in Terminal, I get:
hw.model: MacBookPro17,1

When I use your code and execute:
temp_model_sku = sysctl("hw.model")
print(F"temp_model_sku: {temp_model_sku}")

The output is:
temp_model_sku: b''

When I use the debugger to inspect the sysctl() code, pausing at
if isString:
the value of size is always 0.

Am I doing something wrong?

@mlazovjp Try adding the b prefix to the option names, e.g. b"hw.model"

@mlazovjp Try adding the b prefix to the option names, e.g. b"hw.model"

Kentzo,

Thanks for the assist. I figured it was something I was overlooking. I can confirm that this works properly now after making that change.