Environment variables in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this command?

You run this command in a Linux shell:

echo $HOME

What will it output?

Linux CLI

echo $HOME

A The string "$HOME" literally

B The path to the current user's home directory, e.g., /home/username

C An empty line

D The current working directory path

💡 Hint

Environment variables start with $ and store system info.

The $HOME variable holds the path to the current user's home directory. Using echo $HOME prints that path.

💻 Command Output

intermediate

What does this command output?

Given you run these commands in order:

export MYVAR=hello
echo $MYVAR

What will the second command output?

Linux CLI

export MYVAR=hello
echo $MYVAR

A export MYVAR=hello

B $MYVAR

C An empty line

D hello

💡 Hint

export makes the variable available to child processes.

After exporting MYVAR with value 'hello', echo $MYVAR prints 'hello'.

📝 Syntax

advanced

Which option correctly sets an environment variable for the current shell session?

You want to set an environment variable named PATH_EXT to "/usr/local/bin" for your current shell session only. Which command is correct?

A export PATH_EXT=/usr/local/bin

B PATH_EXT=/usr/local/bin

C set PATH_EXT=/usr/local/bin

D env PATH_EXT=/usr/local/bin

💡 Hint

Use export to make variable available in the current shell.

Only 'export PATH_EXT=/usr/local/bin' sets and exports the variable in the current shell session.

💻 Command Output

advanced

What error does this command produce?

You run this command:

echo $UNDEFINED_VAR

Assuming UNDEFINED_VAR was never set, what is the output?

Linux CLI

echo $UNDEFINED_VAR

A An empty line

B UNDEFINED_VAR

C bash: UNDEFINED_VAR: command not found

D $UNDEFINED_VAR

💡 Hint

Undefined variables expand to empty strings in bash.

If a variable is not set, referencing it with $VAR returns an empty string, so echo prints a blank line.

🚀 Application

expert

How many environment variables are listed by this command?

You run this command in a Linux shell:

env | wc -l

What does the output number represent?

Linux CLI

env | wc -l

A The number of shell functions defined

B The number of files in the current directory

C The number of environment variables currently set

D The number of running processes

💡 Hint

env lists environment variables, wc -l counts lines.

The env command lists all environment variables, and wc -l counts how many lines are output, which equals the number of variables.