[SOLVED] Screen brightness: how can I alter protected (root) files

Question

I have arch log me in as user automatically to X.  But as I am using a laptop, I would like to run the following commands during startup
if grep Discharging <<< "$(acpi)"; then
echo 46 > /sys/class/backlight/intel_backlight/brightness
else
echo 400 > /sys/class/backlight/intel_backlight/brightness
fi
The commands are rejected 'permission denied, even though I can use privileged commands, like blkid, as user.  Apparently it doesn't extend to altering root's files as well.
Can this be done as user?  And if not, which file could I insert these commands so that the brightness level can be set during the boot process?  I've tried /etc/bash.bashrc, but apparently that file is not run until the login has occurred.
Last edited by porphyry5 (2015-03-01 20:16:34)

Answer 1

mychris wrote:Have you read https://wiki.archlinux.org/index.php/Backlight? It covers several different ways to change the backlight.
I tried a variety of methods from this page about 6 months ago, the only one I could get to work automatically was the one I quoted in the first post, and then only if I logged in first as root on tty1 and included the code in /etc/bash.bashrc, and then switched to tty2 to log in as user.
I expected the xbacklight command would do the job in ~/.xinitrc, but it has no effect there, though it works fine after I'm logged into X and set to start work.
I've stayed away from writing udev rules as it looks to require a significant investment of effort to learn and I've not found an example of a conditional rule to follow the pattern of, to avoid investing that effort.
Slackware got me accustomed to simply inserting bash commands into their boot up scripts to produce the effects I wanted, arch seems to be much more restrictive.