Change screen brightness by hour

[jet]

How to change screen brightness by hour?

For as an example one would like the screen have 100 brightness 10:00 and dim it after 20:00 to 75%

Kind regards,
Jan

[apollo]

Screen brightness can be set by pushing a value to a specific file, you may need to look up how your device is named, for me its "amdgpu_bl0".

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/sys/class/backlight/<your_device>/brightness

you can write a short script that pushes a value depending on daytime and let this script execute by a cron job every 15 minutes or whatever you need. i can provide a small sample script later if you need

[jet]

" i can provide a small sample script later if you need"

Yes please, send example.

How to obtain the device screen name? Is there a common alias (for the primary screen) that could be used directly?

Kind regads,
Jan

[fanthom]

Once you figure out the script part you may program cron as described here:
http://porteus-kiosk.org/faq.html#22

[apollo]

A very short sample script could look like this:

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#!/bin/bash
HOUR=`date +%H`

# replace the values with the hours you want to change the brightness
# for easier comparing we use the 24-hours-scheme
if (( $HOUR < 8 )) || (( $HOUR > 13 )); then
    # replace with the required brightness value
    BRIGHT=50
else
    # replace with the required brightness value
    BRIGHT=100
fi

# replace "radeon_bl0" with the corresponding dir on your system
echo $BRIGHT | tee /sys/class/backlight/radeon_bl0/brightness

You need to replace the hours and brightness values to something that matches your need.
Instead of directly tee-ing to a specified file, you could enumerate through the directories in /sys/class/backlight/ and set it for all displays. If i have time later i will add this to the script.

[jet]

Thanks!

Yes, would be very nice to have the script to enumerate through the directories in /sys/class/backlight/

Kind regards,
Jan

[jet]

Once you figure out the script part you may program cron as described here:
http://porteus-kiosk.org/faq.html#22

Hi.
Is there any other way to inject the script to cron?
Can it be loaded and included to Porteus Kiosk thru run_command and wget?

Kind regards,
Jan

[fanthom]

"Can it be loaded and included to Porteus Kiosk thru run_command and wget?"
I believe you could download and replace whole /etc/crontab file with 'run_command='.

Let us know if this method works so i'll update the FAQ.

[jet]

Any help such as exact commands would be helpful.

Thanks

I assume I have to put something like this to run_command=

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wget https://domain.com/files/script.sh -O /home/script.sh; chown -R 1000:1000 /home/script.sh; chmod +X /home/script.sh; echo '* * * * * root su - -c "/home/script.sh" '  >> /etc/crontab;

Kind regards,
Jan

[jet]

That seems not working, any thoughts?

[fanthom]

I though you want to update crontab file.

Anyway - this is enough to run the script:

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wget https://domain.com/files/script.sh -O /home/script.sh; echo '* * * * * root su - -c "sh /home/script.sh"'  >> /etc/crontab;

Mind it will be executed by root every minute.

Also - its better to download files to /opt as /home may be refreshed (depends on your persistence level).

[jet]

Hi. Thanks!

The executing seems to work, but I think permissions (and owner?) should be changed for /sys/class/backlight/ to be able to read and modify the brightness file?

[fanthom]

With this configuration:

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* * * * * root

You have instructed the cron to run the command as root.

You may add following line to your script to confirm this:

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whoami >> /opt/script.log

[jet]

Thanks!

Found out that there was a missing $-sign in my script and there were some other issues too..

Now finally got it up and running!

Kind regards,
Jan

[jet]

Hi.
How to close and restart the browser (Chrome) from a script?