python with echo
Diez B. Roggisch
deets at nospam.web.de
Thu Nov 12 11:41:12 CET 2009
hong zhang schrieb:
> I have a question of python using echo.
> POWER = 14
> return_value = os.system('echo 14 > /sys/class/net/wlan1/device/tx_power')
> can assign 14 to tx_power
> return_value = os.system('echo $POWER > /sys/class/net/wlan1/device/tx_power')
> return_value is 256 not 0. It cannot assign 14 to tx_power.
Because $POWER is an environment-variable, but POWER is a
python-variable, which isn't magically becoming an environment variable.
There are various ways to achieve what you want, but IMHO you should
ditch the whole echo-business as it's just needless in python itself:
with open("/sys/class/net/wlan1/device/tx_power", "w") as f:
f.write("%i" % POWER)
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