C style arithmetic with floating point values in Bash

Question

How can I have the right result from this bash script?

#!/bin/bash
echo $(( 1/2 ))

I get 0 as result! So I tried to use these but without success:

$ echo $(( 1/2.0 ))
bash: 1/2.0 : syntax error: invalid arithmetic operator (error token is ".0 ")
$ echo $(( 1.0/2 ))
bash: 1.0/2 : syntax error: invalid arithmetic operator (error token is ".0/2 ")

Answer 1

bash is not the right tool alone to use floats, you should use bc with it :

bc <<< "scale=2; 1/2"
.50

If you need to store the result in a variable :

res=$(bc <<< "scale=2; 1/2")
echo $res