Script to prevent screen blanking using "mouse move" doesn't work

Question

This is my attempt to make a script that will use a "mouse move" to prevent screen blanking while watching videos. I'm hoping to use the value for highest CPU% process in top and if CPU usage exceeds 5%, a mouse move should occur.

#!/usr/bin/env bash

sleep_period=60s 

while true; do
  if (( $(top -bn 1 | sed -nrs '8p' | awk '{ print $9 }') -gt 5 )); then 
    while (( $(top -bn 1 | sed -nrs '8p' | awk '{ print $9 }') -gt 5 )); do
      xdotool mousemove 0 100
      xdotool mousemove 0 50
      sleep ${sleep_period}
    done
  else
    sleep ${sleep_period}
  fi
done

Unfortunately, it does not work. The errors are like this:

[07:20 PM] /bin $ noo.sh
/home/vasa1/bin/noo.sh: line 6: ((: 0.0 -gt 5 : syntax error: invalid arithmetic operator (error token is ".0 -gt 5 ")
/home/vasa1/bin/noo.sh: line 6: ((: 6.4 -gt 5 : syntax error: invalid arithmetic operator (error token is ".4 -gt 5 ")

How do I fix this? (Please note that I'm not experienced in scripting.)

---

Based on answers here, I put together:

#!/usr/bin/env bash

sleep_period=5m 

while true; do
  if [[ $(top -bn 1 | sed -nrs '8p' | awk '{ print int($9) }') -gt 8 ]]; then 
    while [[ $(top -bn 1 | sed -nrs '8p' | awk '{ print int($9) }') -gt 8 ]]; do
      xset -dpms; xset s off
      xset +dpms; xset s on
      sleep ${sleep_period}
    done
  else
    sleep ${sleep_period}
  fi
done

Then, I reported this code over at Ubuntu Forums and Vaphell worked on it further. Below is Vaphell's version and is what I am using:

#!/usr/bin/env bash

sleep_period=5m 

while true; do
  if top -bn 1 | awk 'NR==8 { exit !($9>8); }'; then
    xset -dpms; xset s off
    xset +dpms; xset s on
  fi
  sleep ${sleep_period}
done

Answer 1

You can use

xset -dpms; xset s off

to stop the screen from going black.

To enable this again use

xset +dpms; xset s on

So -dpms disables the the power energy saving features, which can turn off the whole monitor and s off turns off the screen saver feature of the X server.

This does not work with the xscreensaver, which was mentioned in the comments.

Answer 2

You have a couple of issues, first, you will need 2 iterations of top each time, see my answer here and the bug report here.

The other problem is that bash does not do floating point, so if your CPU usage is something like 6.2, the .2 will break the script. Bash is simply not designed for 'complex' arithmetic operations. One way around this would be to move the >5 check inside your awk command:

#!/usr/bin/env bash

sleep_period=60s 

while true; do
    until top -bn 2 -d 0.01 | sed -nrs '8p' | awk '{if($9>5){exit 1}else{exit 0}}'; do
      xdotool mousemove 0 100
      xdotool mousemove 0 50
      sleep ${sleep_period}
    done
   sleep ${sleep_period}
done

Answer 3

First, you need to install xdotool & rand. Example on Ubuntu:

sudo apt install xdotool rand

Then run this one-liner in a terminal (as user):

eval $(xdotool getdisplaygeometry --shell); while true; do xdotool mousemove `rand -M $WIDTH` `rand -M $HEIGHT` && sleep $((`rand -M 300` + 120)); done;