How to add values in UNIX?

Question

I am new to Unix. I tried to add values as mentioned below:

var='expr 2 + 2'
echo "Total value: $var"

I expect the output to be Total value: 4. Instead I am getting Total value: expr 2 + 2.

Could anyone help me to identify my mistake?

Answer 1

Simplified approach :

var=$((2 + 2))

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Or bc (calculator language) approach to perform math calculations:

var=$(echo '2 + 2' | bc)
echo "Total value: $var"
Total value: 4