Array slicing in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is array slicing in bash scripting?

Array slicing is a way to extract a part of an array by specifying a start index and length, similar to cutting a piece from a list.

beginner

How do you slice an array named arr from index 2 to get 3 elements?

Use ${arr[@]:2:3}. This extracts 3 elements starting from index 2.

intermediate

What happens if the length in array slicing is omitted in bash?

If length is omitted, slicing extracts all elements from the start index to the end of the array.

beginner

Given arr=(a b c d e), what is the output of echo ${arr[@]:1:2}?

The output is b c. It slices 2 elements starting from index 1.

intermediate

Can array slicing in bash use negative indices?

Yes, negative start indices count from the end of the array backwards. For example, ${arr[@]: -2} gets the last two elements.

In bash, what does ${arr[@]:3} do?

A Extracts all elements starting from index 3 to the end

B Extracts the first 3 elements

C Extracts 3 elements starting from index 0

D Extracts 3 elements starting from index 3

Without length, slicing extracts from the start index (3) to the end.

How do you get the last 2 elements of an array arr in bash?

A ${arr[@]: -2}

B ${arr[@]:2:2}

C ${arr[@]:-1}

D ${arr[@]:0:2}

Negative start index counts from the end; -2 means last two elements.

What is the index of the first element in a bash array?

A 1

B -1

C 0

D Depends on array size

Bash arrays start indexing at 0.

If arr=(x y z), what does ${arr[@]:1:5} return?

A z

B y z

C x y z

D Error

Length longer than available elements returns all from start index without error.

Which syntax correctly slices an array arr from index 0 for 2 elements?

A ${arr:0:2}

B ${arr[0]:2}

C ${arr[2]:0}

D ${arr[@]:0:2}

Correct syntax uses ${arr[@]:start:length}.

Explain how to extract a slice from a bash array and what happens if the length is omitted.

Think about cutting a piece from a list starting at a position.

Describe how negative indices work in bash array slicing and give an example.

Negative numbers count backwards from the end.