expr Arithmetic

 

#!/bin/bash
#expr

My_var1 = 12 is 
my_var2 = . 3 
# expr 　is the command
MY_VAR3=`expr $MY_VAR1 + $MY_VAR2`
MY_VAR4=`expr $MY_VAR1 \* $MY_VAR2`
MY_VAR5="$MY_VAR1 + $MY_VAR2"
echo $MY_VAR3
echo $MY_VAR4
echo $MY_VAR5

Output:

15
36
12 + 3