Why can't I use
echo $1 > /sys/class/backlight/acpi_video0/brightness in a simple bash script?
It gives me the error:
echo: write error: Invalid argument.
I bet the shell is expanding $1 and thus echo thinks it is receiving a bunch of arguments, rather than a string.
You should check what the actual value of
At a glance, it appears that it accepts an integer in the range 0 to 8 (for me at least).