Floating-point division in bash

Question

I\'m trying to convert whatever numbers the user inputs into 2 decimal places. For instance

What is the total cost in cents? 2345
output: 23.45

Answer 1

Perhaps it's nostalgia for reverse polish notation desk calculators, but I'd use dc rather than bc here:

dc <<<"2 k $cost_in_cents 100 / p"

Output is, properly, a float (with two digits past the decimal point of precision).

The exact same code, with no changes whatsoever, will work to convert 20 to .20.

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See BashFAQ #22 for a full discussion on floating-point math in bash.