if-then-fi structure in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the if-then-fi structure in bash scripting?

It allows the script to make decisions by running commands only if a certain condition is true.

beginner

Write the basic syntax of an if-then-fi statement in bash.

if [ condition ]; then<br> commands<br>fi

beginner

In bash scripting, what does the fi keyword do?

It marks the end of the if block, telling the shell that the conditional commands are finished.

intermediate

How do you check if a file exists using if-then-fi in bash?

if [ -e filename ]; then<br> echo "File exists"<br>fi

beginner

Why is it important to have spaces around the square brackets in if [ condition ]?

Because [ is a command and needs spaces to separate it from the condition and brackets, otherwise the shell will give an error.

What keyword ends an if block in bash scripting?

A fi

B end

C done

D stop

The fi keyword is used to close an if block in bash.

Which of these is the correct way to start an if statement in bash?

A if ( condition ) then

B if [ condition ]; then

C if { condition } then

D if condition then

The correct syntax uses square brackets with spaces and a semicolon before then: if [ condition ]; then.

What happens if the condition in an if statement is false?

A The commands inside <code>then</code> run

B The script restarts

C The script stops immediately

D The commands inside <code>then</code> do not run

If the condition is false, the commands inside the then block are skipped.

Which symbol is used to test conditions inside the if statement?

A []

B ()

C {}

D <>

Square brackets [] are used to test conditions in bash if statements.

How do you write an if statement that checks if a variable x equals 5?

A if [ $x == 5 ]; then

B if ( $x = 5 ) then

C if [ $x = 5 ]; then

D if $x == 5 then

In bash, use single equals = inside square brackets with spaces: if [ $x = 5 ]; then.

Explain how the if-then-fi structure works in bash scripting.

Think about how you decide to do something only if a condition is met.

Write a simple bash script using if-then-fi to check if a file named 'data.txt' exists and print a message.

Use the -e option inside the condition to check for file existence.