How to convert string to integer in UNIX

Question

I have d1=\"11\" and d2=\"07\". I want to convert d1 and d2 to integers and perform d1-d2. How do I do this

Answer 1

The standard solution:

 expr $d1 - $d2

You can also do:

echo $(( d1 - d2 ))

but beware that this will treat 07 as an octal number! (so 07 is the same as 7, but 010 is different than 10).