What methods can be used to do arithmetic evaluations in bash?

shoebill

You can use the builtin let or ((...))

For producing the result from the expression use $((...))

e.g:

$ mynumber=5
$ let "mynumber=$mynumber + 1"
$ echo $mynumber
6

Help on the let builtin can be obtained using:

$ builtin help let

Using ((...)) arithmetic evaluation in a bash script, you will see this syntax used in for and while loops.

StartingNumber=$(($StartNumber < 10))