using terminal commands results in variable does not work in PYTHON

kottes

I am trying to read the brightness parameter of blue Led of omega2 to use it in a variable to use this to manage a led in my frontplate of my box with omega 2lte. I do not know what i do wrong. here is the essential part of the python script I use:

while True:
w = os.system("cat /sys/class/leds/omega2lte:blue:wifi/brightness")
if w == 255:
status2 = "connected"
status = gpioObj.setValue(0)
print(status2)

The frontplate shows if I am connected to my application via mobile ( iot ) or via wifi, if there is no good radio connection to mobile iot
If I look in logread I see that the cat command shows the correct value of 255 and but the ïf in the programm does not see the variable.
Van some body help me with this?

tjoseph1

@kottes
Looks like os.system() is not passing the result of cmd to w.

Try this:

import subprocess
cmd = "cat /sys/class/leds/input3::numlock/brightness"
ret = subprocess.check_output(cmd, shell = True).strip()
if ret == b'1':
print("NumLock ON")

Thanks.

victoriano

Why don't you just read the (pseudo) file? No need to open new processes. Using

w = int(open('/sys/class/leds/omega2lte:blue:wifi/brightness').read())

Will give you what you need from python in a pythonic way.