Section 6.8. Arithmetic

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6.8. Arithmetic

To perform an arithmetic operation in Bash, you simply put the operation inside a double set of parentheses (Figure 6-24).

(( operation ))

Common numeric operations include those listed in Figure 6-25.

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Figure 6-25. Arithmetic operators.

+ -	Addition, subtraction.
++ --	Increment, decrement.
* / %	Multiplication, division, remainder.
**	Exponentiation.

Integer arithmetic is faster than floating-point arithmetic. If you know your variable will always be an integer (like a counter or array index), you can use the declare built-in to declare it to be an integer (Figure 6-26).

Shell command: declare -i name

This form of declare defines the variable name as an integer value

After we look at some simple conditional expressions, we'll combine them into a simple math script.