Subtract two variables in Bash

Question

I have the script below to subtract the counts of files between two directories but the COUNT= expression does not work. What is the correct syntax?

<         


        

Answer 1

Try this Bash syntax instead of trying to use an external program expr:

count=$((FIRSTV-SECONDV))

BTW, the correct syntax of using expr is:

count=$(expr $FIRSTV - $SECONDV)

But keep in mind using expr is going to be slower than the internal Bash syntax I provided above.