Arithmetic expansion $(( )) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the arithmetic expansion syntax $(( )) do in bash scripting?

It allows you to perform arithmetic calculations inside the double parentheses and returns the result as a number.

beginner

How would you add two numbers, 5 and 3, using arithmetic expansion in bash?

You write $((5 + 3)). This will output 8.

beginner

Can you use variables inside $(( )) for arithmetic operations?

Yes, you can use variables without the $ sign inside $(( )). For example, if a=4 and b=2, then $((a * b)) will output 8.

intermediate

What happens if you try to use floating point numbers inside $(( )) in bash?

Bash arithmetic expansion only supports integers. Using floating point numbers will cause errors or unexpected results.

beginner

How can you assign the result of an arithmetic expansion to a variable in bash?

You can assign it like this: result=$((expression)). For example, result=$((5 + 3)) assigns 8 to the variable result.

What will the command echo $((10 / 3)) output in bash?

A 3

B 3.3333

C 4

D Error

Bash arithmetic expansion only works with integers, so it performs integer division and outputs 3.

Which of the following is the correct way to multiply two variables a and b in bash using arithmetic expansion?

A echo $(( a * b ))

B echo $(( $a * $b ))

C echo $[a * b]

D echo $((a + b))

Inside $(( )), variables are referenced without the $ sign. So $(( a * b )) is correct.

What will echo $((2 ** 3)) output in bash?

A Error

B 6

C 9

D 8

The ** operator means exponentiation. 2 to the power of 3 is 8.

Which of these is NOT supported inside arithmetic expansion $(( )) in bash?

A Addition (+)

B Floating point division

C Subtraction (-)

D Modulo (%)

Bash arithmetic expansion only supports integer math, so floating point division is not supported.

How do you assign the result of 7 + 5 to a variable named sum in bash?

A sum=7+5

B sum=$7+5

C sum=$((7 + 5))

D sum=$(7 + 5)

You must use arithmetic expansion $(( )) to calculate the sum and assign it to the variable.

Explain how to use arithmetic expansion $(( )) in bash to perform basic math operations with variables.

Think about how you write math expressions inside the double parentheses and how variables are referenced.

Describe the limitations of arithmetic expansion $(( )) in bash and how it handles division.

Consider what happens when you divide numbers that don't divide evenly.