xrandr --output LVDS-1 --brightness $(bc -l <<<"$(sed 's/Brightness: //' <<<$(xrandr --prop --verbose | grep Brightness)) $(if [ "$1" = "+" ];then echo +;else echo -;fi) 0.1")
I currently have this code set up to a keyboard shortcut in XFCE on my Arch system, and it works great to adjust brightness up or down 0.1 notches. Only problem is, it's slow enough to take a second or so to execute, and pressing multiple times is worse and can slow the whole computer a bit.
How would you improve the code? (I'm pretty new to shell scripting, so I'm also partly asking this to see the process by which code I write cold be optimized.)
EDIT: Okay, so I followed drewbenn's suggestion of profiling and got this:
time xrandr -q --verbose > /dev/null
The query, then, was the biggest issue. I changed it so that it would store the current brightness level in a file somewhere and the shortcut keys would run the following code:
#!/bin/bash val=$(cat ~/.bright_key_folder/lvl) if ( [ "$1" == "+" ] && [[ $(bc -l ~/.bright_key_folder/lvl xrandr --output LVDS-1 --brightness $(cat ~/.bright_key_folder/lvl) elif ( [ "$1" == "-" ] && [[ $(bc -l 0") == 1 ]] ) then bc -l ~/.bright_key_folder/lvl xrandr --output LVDS-1 --brightness $(cat ~/.bright_key_folder/lvl) fi
Then on startup it resets brightness and the file value both to 1.