https://www.learnshell.org/en/Hello,_World!
Basic arithmetic Operations
Simple arithmetics on variables can be done using the arithmetic expression: $((expression))
A=3
B=$((100 * $A + 5)) # 305
#you just can't do like this:
C=$a+3
#Because if you try to echo it the result will be 3+3 as textThe basic operators are:
a + b addition (a plus b)
a – b substraction (a minus b)
a * b multiplication (a times b)
a / b division (integer) (a divided by b)
a % b modulo (the integer remainder of a divided by b)
a ** b exponentiation (a to the power of b)