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Adjust gamma so monitor doesn't mess up your body's clock

Terminal - Adjust gamma so monitor doesn't mess up your body's clock
xrandr | sed -n 's/ connected.*//p' | xargs -n1 -tri xrandr --output {} --brightness 0.7 --gamma 2:3:4
2010-10-24 10:45:57
User: hackerb9
Functions: sed xargs
Adjust gamma so monitor doesn't mess up your body's clock

[UPDATE: Now works for multiple connected outputs]

I woke up around midnight with an urge to do some late night hacking, but I didn't want a bright monitor screwing up my body's circadian rhythm. I've heard that at night blue (short wavelength) lights are particularly bad for your diurnal clock. That may be a bunch of hooey, but it is true that redder (longer wavelength) colors are easier on my eyes at night.

This command makes the screen dimmer and adjusts the gamma curves to improve contrast, particularly darkening blues and greens (Rɣ=2, Gɣ=3, Bɣ=4). To reset your screen to normal, you can run this command:

xrandr | sed -n 's/ connected.*//p' | xargs -n1 -tri xrandr --output {} --brightness 1 --gamma 1:1:1

or, more briefly,

xgamma -g 1

Note: The sed part is fragile and wrong. I'm doing it this way because of a misfeature in xrandr(1), which requires an output be specified but has no programmatic way of querying available outputs. Someone needs to patch up xrandr to be shell script friendly or at least add virtual outputs named "PRIMARY" and "ALL".


Todo: Screen should dim (gradually) at sunset and brighten at sunrise. I think this could be done with a self-resubmitting at job, but I'm running into the commandlinefu 127 character limit just getting the sunrise time:

wget http://aa.usno.navy.mil/cgi-bin/aa_pap.pl --post-data=$(date "+xxy=%Y&xxm=%m&xxd=%d")"&st=WA&place=Seattle" -q -O- | sed -rn 's/\W*Sunrise\W*(.*)/\1/p'

I hope some clever hacker comes up with a command line interface to Google's "OneBox", since the correct time shows up as the first hit when googling for "sunrise:cityname".


[Thank you to @flatcap for the sed improvement, which is much better than the head|tail|cut silliness I had before. And thank you to @braunmagrin for pointing out that the "connected" output may not be on the second line.]


There is 1 alternative - vote for the best!

Terminal - Alternatives

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What others think

Hey this is a really cool idea. I have thought about something similar, but never really knew how to do it. You said you were running out of room on CLF's 127 character business. If you figure out how to do the dimming will you send it to me? Thanks!

Comment by thingsgoboom 230 weeks and 6 days ago

Let me try that again.

Redshift, works great for this.


Comment by binarysys 230 weeks and 5 days ago

All that nonsense:

head -2 | tail -1 | cut -f1 -d' '

can be simplified to:

sed -n '2{s/ .*//;p}'


sed -n # don't output anything 2{...;...} # when you get to line 2 perform some commands s/ .*// # search for a space and other stuff, replace with nothing p # print the result
Comment by flatcap 230 weeks and 5 days ago

Maybe you could use:

`xrandr | grep "[^s]connected"` instead.

This searches in the output of xrandr for the output that is connected, which may not be in the second line.

Comment by braunmagrin 230 weeks and 3 days ago

I`m sorry.

xrandr on Ubuntu 10.04 doesn't have the brightness option.

Try to use this instead, it works even if the connected output isn't in the second line.

xrandr --output `xrandr | grep "[^s]connected" | cut -f1 -d' '` --gamma 2:3:4

"grep [^s]connected" searches for a expression that contains "connected" with any character before, besides 's' (from "disconnected").

Comment by braunmagrin 230 weeks and 3 days ago

@braunmagrin: Fair enough. Try this:

sed -n '/ connected/{s/ .*//;p}'

Fewer characters and only one process started rather than two.

Comment by flatcap 229 weeks and 6 days ago

@flatcap, @braunmagrin thanks for the tips!

@thingsgoboom here are a pair of self-resubmitting scripts which set the gamma appropriately and then use "at" to schedule the other script to run. Put the contents of these into files in your path (e.g., your home directory), mark them executable, and then run one of them. As long as you stay logged on, they will keep running each other at the correct time.



xrandr \ | sed -n 's/ connected.*//p' \ | xargs -n1 -tri xrandr --output {} --brightness 0.7 --gamma 2:3:4 \ || exit 1 echo `env` daytime.sh | at $(wget http://aa.usno.navy.mil/cgi-bin/aa_pap.pl --post-data=$(date "+xxy=%Y&xxm=%m&xxd=%d")"&st=WA&place=Seattle" -q -O- | sed -rn 's/.*Sunrise\W*(.*)/\1/p' | tr -d . ) >/dev/null 2>&1



xgamma -q -g 1 || exit 1 echo `env` nighttime.sh | at $(wget http://aa.usno.navy.mil/cgi-bin/aa_pap.pl --post-data=$(date "+xxy=%Y&xxm=%m&xxd=%d")"&st=WA&place=Seattle" -q -O- | sed -rn 's/.*Sunset\W*(.*)/\1/p' | tr -d . ) >/dev/null 2>&1


You'll have to remove the $ from the front of each line, of course. I only put it there because that's the only way commandlinefu lets me markup that something is code.

Comment by hackerb9 229 weeks and 4 days ago

Your point of view

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