until loop in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does an until loop do in Bash scripting?

An until loop runs the commands inside it repeatedly until the given condition becomes true. It keeps running while the condition is false.

beginner

How is an until loop different from a while loop?

A while loop runs while the condition is true. An until loop runs while the condition is false, stopping when it becomes true.

beginner

Write the basic syntax of an until loop in Bash.

until [ condition ] do commands done

beginner

What will this script print?

count=1
until [ $count -gt 3 ]
do
  echo $count
  ((count++))
done

It will print: 1 2 3 The loop runs until count is greater than 3, so it prints 1, 2, and 3.

intermediate

Why might you choose an until loop instead of a while loop?

You use until when you want to repeat commands until a condition becomes true. It can make your code easier to read if you think in terms of "keep going until this happens."

What condition causes an until loop to stop running?

A When the condition becomes true

B When the condition becomes false

C After one iteration

D Never stops

An until loop runs while the condition is false and stops when it becomes true.

Which of these is the correct syntax to start an until loop?

A while [ condition ]; do

B until [ condition ]; do

C for i in [ condition ]; do

D if [ condition ]; then

The until loop starts with until [ condition ]; do.

What will this script print?

count=5
until [ $count -lt 3 ]
do
  echo $count
  ((count--))
done

A Nothing

B 3 4 5

C 1 2 3

D 5 4 3

The loop runs until count is less than 3, so it prints 5, 4, and 3.

Which loop runs while the condition is true?

A until loop

B none

C while loop

D both until and while

A while loop runs while the condition is true.

What happens if the condition in an until loop is true at the start?

A The loop does not run at all

B The loop runs forever

C The loop runs once

D The loop runs twice

If the condition is true at the start, the until loop does not run.

Explain how an until loop works in Bash and give a simple example.

Think about repeating something until a condition becomes true.

Compare and contrast until and while loops in Bash scripting.

Focus on when each loop continues and stops.