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

You can use:

((count = FIRSTV - SECONDV))

to avoid invoking a separate process, as per the following transcript:

pax:~$ FIRSTV=7
pax:~$ SECONDV=2
pax:~$ ((count = FIRSTV - SECONDV))
pax:~$ echo $count
5