Question on Redshift and no internet access.
 

Hi.

If I setup Redshift with a custom config (with lat & long) file on a computer with no internet access - how would it know when is daylight and nighttime? I know that without the ~/.config/redshift.conf file - it detects coordinates, etc. when I go online.

Thanks.

Maybe from system time or hardware clock time? I only tried Redshift briefly a while ago, wasn't keen on it.

Hi Brian. But if it got the time from the PC - how would it determine the time of year? For example night mode would have kick in far sooner in Autumn-Winter.

What did you not like about RS?

I am only guessing that it uses some type of solar calculator to determine sunrise/sunset times based upon position.


https://www.esrl.noaa.gov/gmd/grad/solcalc/

Hi Michael. That sounds about right.

I've certainly been sleeping better after using Redshift.

I've come across another handy blue light app - it does not need internet access.

Example usage for eve/nighttime:

Edit:

RS can be used in a similar manner:

I tried both of these (seperately) in crontab (to run at 9pm every night) but both never ran. Does anyone know why?

Edit: I verified that cron was running with:

Try using the absolute path to each program.

Hi Michael.

I tried both of these but no joy:

Are you using a users or system cron job?

Users since I don't need to run those commands as root.

I am not familiar with either program and I don't think sct has any sort of configuration file. Since a cron job is not attached to the display you might need to add a export DISPLAY=:0

10 11 * * * export DISPLAY=:0 && /usr/bin/sct 3500

Cheers Michael. That works! I presume the same applies to Redshift - I no longer have it installed (did a fresh reinstall of Debian 9.4 recently) but if someone else wants to try.

Edit: It also works without the full path, like so: