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?

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Answer 1

For simple integer arithmetic, you can also use the builtin let command.

 ONE=1
 TWO=2
 let "THREE = $ONE + $TWO"
 echo $THREE
    3

For more info on let, look here.

Answer 2

This is how I always do maths in Bash:

count=$(echo "$FIRSTV - $SECONDV"|bc)
echo $count