Some more bash optimizations

[rany2]

The below changes reduces CPU usage by 0.5% on my X86 machine:

• Switch to using : instead of true as it is consistently faster in the below benchmark, unsure why as they are both noops:

  • timeout 3 bash -c 'while :; do true; echo y; done'
  • wc -l 1881683
  • timeout 3 bash -c 'while :; do :; echo y; done'
  • wc -l 2152695

• Switch to switch case for the idle/sleep function handling code.

• Remove unneded non-empty string handling check

[lynxthecat]

I came across this:

https://lobste.rs/s/1l1t8f/bash_functions_are_better_than_i_thought

With some functions like log_msg() there are conditionals that are repeatedly (and unnecessarily) reevaluated. It might be beneficial to either (re)define the functions based on the conditionals on the initial script load and/or leverage formulations like ‘${function} argument(s)’ in which the function is changed in dependence upon the conditionals.

[rany2]

@lynxthecat I've thought of this actually but got lazy. I'm not sure how beneficial it would be to do this but I could look into it

[lynxthecat]

Very nice changes! I am seeing more frequent and more prolonged dips down to 6% total CPU usage on my RT3200 now (as measured using atop 2 and hitting p):