Array slicing in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Bash array slicing?

Given the array arr=(a b c d e f g), what is the output of echo ${arr[@]:2:3}?

Bash Scripting

arr=(a b c d e f g)
echo ${arr[@]:2:3}

A d e f

B b c d

C a b c

D c d e

💡 Hint

Remember that array slicing starts at index 0 and the syntax is ${array[@]:start:length}.

The slice starts at index 2 (third element) and takes 3 elements: c, d, e.

💻 Command Output

intermediate

What does this negative index slice output?

With arr=(1 2 3 4 5 6 7 8 9), what is the output of echo ${arr[@]: -4:2}?

Bash Scripting

arr=(1 2 3 4 5 6 7 8 9)
echo ${arr[@]: -4:2}

A 8 9

B 6 7

C 7 8

D 5 6

💡 Hint

Negative start index counts from the end of the array.

Start index -4 means start at the 4th last element, which is 6, then take 2 elements: 6 and 7.

📝 Syntax

advanced

Which option correctly slices the last 3 elements of an array?

Given arr=(x y z a b c d), which command outputs the last 3 elements?

Bash Scripting

arr=(x y z a b c d)

A echo ${arr[@]: -3:3}

B echo ${arr[@]:3:3}

C echo ${arr[@]: -3}

D echo ${arr[@]: -4:3}

💡 Hint

Use negative start index and specify length to get exact elements.

Option A starts 3 from the end and takes 3 elements, correctly outputting 'b c d'. Option A omits length and outputs 3 elements but may be ambiguous. Option A starts at index 3, which is 'a', not last 3. Option A starts 4 from end and takes 3 elements, which is 'a b c'.

🔧 Debug

advanced

Why does this slicing command fail?

Given arr=(10 20 30 40 50), why does echo ${arr[@]:-3:2} produce unexpected output?

Bash Scripting

arr=(10 20 30 40 50)
echo ${arr[@]:-3:2}

A Because the syntax ${arr[@]:-3:2} is interpreted as a default value, not slicing

B Because negative indices must have a space after the colon to be recognized

C Because there is no space after the colon before the negative index

D Because the array is too short for this slice

💡 Hint

Check how Bash interprets the colon and minus sign in parameter expansion.

Without a space, ${arr[@]:-3:2} is interpreted as 'if arr[@] is unset or null, use -3:2', not slicing. To slice with negative index, a space is needed after the colon: ${arr[@]: -3:2}.

🚀 Application

expert

How many elements are in the slice?

Given arr=(alpha beta gamma delta epsilon zeta eta), what is the number of elements output by echo ${arr[@]:4:10}?

Bash Scripting

arr=(alpha beta gamma delta epsilon zeta eta)
echo ${arr[@]:4:10}

A 4

B 7

C 3

D 10

💡 Hint

The slice length can be longer than the remaining elements, but output only includes available elements.

Starting at index 4 (epsilon), there are only 3 elements left: epsilon, zeta, eta. The length 10 is more than available, so only 3 elements are output.