Re: Can Bash do simple math?

[bash]

On Mon, Aug 05, 2024 at 07:10:05PM -0400, Greg Wooledge wrote:
> My first comment is that by using all-caps variable names, you're stepping
> on internal variables that bash uses for its own purposes.  SECONDS has
> a special meaning.  [...] 
> Avoid all-caps variable names for precisely this reason.
> 
This is very helpful. I always did uppercase variable names in Bash as I
thought this was the "standard way" of naming variables. Guess I should
reconsider!

> I wonder if the bug you're seeing goes away if you rename your variables.
> 
It does! I have lowered the case of all variables in the script and run
the test for almost 8 million rounds without any errors. 

> I wonder if your bug goes away if you stop calling the function in a
> command substitution.  Something like this, perhaps:
>
No, it doesn't. Using your code but with a uppercase $SECONDS variable
name an error was produced after some 70k rounds:

70700 processed.
Round 70760 unexpected result: 1:1:36

With the $SECONDS variable lowercase, however, the script runs to
completion without any errors.

> 
> If this doesn't generate errors, but your original does, then you'll have
> to figure out which one of my changes made the errors go away.
>
My guess is that the $SECONDS variable was updated by Bash _after_ my
assignment but _before_ the printf command, resulting in a "erroneous"
value being printed. A kind of race condition, perhaps :)

I appreciate your help in realising what I did wrong and the pointers to
improve my scripting in the future! Thanks :)