SHELL

bash expression

let a=1 #(outside for loop)

for i in {0..100..10} # example
do
	let a=a+5
	echo $a
done

bash expression

gamma_new="$(($gamma_t-360))"
num2="$(($num1+num2))"

$((expression))

$a=5

yourname_$(($a-1))
#will give
yourname_4