Environment variables in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to display the value of the HOME environment variable.

Linux CLI

echo $[1]

Drag options to blanks, or click blank then click option'

AHOME

BPATH

CUSER

DSHELL

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names like PATH or USER instead of HOME.

Forgetting the dollar sign ($) before the variable name.

The HOME environment variable stores the path to the current user's home directory. Using echo $HOME prints this path.

2fill in blank

medium

Complete the code to set a new environment variable named MY_VAR with the value 'hello'.

Linux CLI

export [1]='hello'

Drag options to blanks, or click blank then click option'

AMY_VAR

BVAR

CHELLO

DMYVAR

Attempts:

3 left

💡 Hint

Common Mistakes

Not using export so the variable is not available to other programs.

Using lowercase or incorrect variable names.

To create an environment variable, use export followed by the variable name and its value. Here, MY_VAR is the variable name.

3fill in blank

hard

Fix the error in the code to append ':~/bin' to the PATH environment variable.

Linux CLI

export PATH=$PATH:[1]

Drag options to blanks, or click blank then click option'

A$PATH

B~/bin

CPATH

D$PATH:

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'PATH' without the dollar sign, which treats it as a string.

Placing the colon in the wrong place.

Not using the tilde (~) for the home directory.

To add a directory to PATH, prepend or append the directory path. Here, ~/bin is the directory to add. The correct syntax is export PATH=$PATH:~/bin.

4fill in blank

hard

Fill both blanks to create a variable named COUNT with value 5 and print it.

Linux CLI

export [1]=[2]
echo $COUNT

Drag options to blanks, or click blank then click option'

ACOUNT

B5

C10

DVALUE

Attempts:

3 left

💡 Hint

Common Mistakes

Putting spaces around the equals sign.

Using the wrong variable name or value.

First, set the variable name COUNT to the value 5 using export. Then, echo $COUNT prints the value.

5fill in blank

hard

Fill all three blanks to create a variable named USERNAME with the current user and print a greeting.

Linux CLI

export [1]=$(whoami)
echo "Hello, $[2]! Your shell is $[3]."

Drag options to blanks, or click blank then click option'

AUSERNAME

CSHELL

DUSER

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in export and echo.

Forgetting to use command substitution with $(whoami).

Using USER instead of SHELL for the shell variable.

Set USERNAME to the current user using $(whoami). Then print a greeting using $USERNAME and the SHELL environment variable.

Practice

1. What is the purpose of environment variables in a Linux shell?

easy

A. To speed up the internet connection

B. To store settings that programs can use during execution

C. To permanently delete files from the system

D. To create new user accounts automatically

Solution

1. Step 1: Understand environment variables

   Environment variables hold information like settings or preferences that programs can read while running.

2. Step 2: Identify the correct purpose

   Among the options, only storing settings matches the role of environment variables.

3. Final Answer:

   To store settings that programs can use during execution -> Option B

4. Quick Check:

   Environment variables = store settings [OK]

Hint: Remember: environment variables hold settings, not files or users [OK]

Common Mistakes:

• Confusing environment variables with file operations
• Thinking environment variables control hardware
• Assuming environment variables create users

2. Which command correctly sets an environment variable named MY_VAR with value hello for the current shell and its child processes?

easy

A. declare MY_VAR hello

B. set MY_VAR=hello

C. env MY_VAR hello

D. export MY_VAR=hello

Solution

1. Step 1: Recall how to set environment variables

   In Linux shells, export is used to set environment variables for the current shell and its children.

2. Step 2: Check each command

   set MY_VAR=hello is incorrect syntax; env MY_VAR hello does not set variable persistently; declare MY_VAR hello is invalid for environment variables.

3. Final Answer:

   export MY_VAR=hello -> Option D

4. Quick Check:

   Use export to set environment variables [OK]

Hint: Use 'export' to set environment variables for shell and children [OK]

Common Mistakes:

• Using 'set' instead of 'export' to set environment variables
• Trying to set variables without export, so children don't see them
• Confusing 'env' command usage

3. Given the commands below, what will be the output of echo $GREETING?

GREETING="Hello"
export GREETING
GREETING="Hi"
echo $GREETING

medium

A. Hello

B. $GREETING

C. Hi

D. Error: variable not found

Solution

1. Step 1: Understand variable assignment and export

   First, GREETING is set to "Hello" and exported, making it available to child processes. Then GREETING is reassigned to "Hi" in the current shell.

2. Step 2: Determine the value echoed

   The echo command prints the current value of GREETING, which is "Hi" after reassignment.

3. Final Answer:

   Hi -> Option C

4. Quick Check:

   Variable reassignment updates value = Hi [OK]

Hint: Last assignment before echo is the value printed [OK]

Common Mistakes:

• Thinking export freezes the variable value
• Expecting the first assigned value to print
• Confusing export with immediate output

4. What is wrong with this script snippet if the goal is to set PATH to include /usr/local/bin?

PATH=$PATH:/usr/local/bin
export PATH

medium

A. Nothing is wrong; it correctly appends to PATH

B. It should use export PATH=$PATH:/usr/local/bin in one line

C. It overwrites PATH instead of appending

D. It should prepend /usr/local/bin before $PATH

Solution

1. Step 1: Analyze the PATH modification

   The script appends :/usr/local/bin to the existing PATH variable, which is a common way to add directories.

2. Step 2: Check export usage

   Exporting PATH after assignment makes the new value available to child processes. This is correct usage.

3. Final Answer:

   Nothing is wrong; it correctly appends to PATH -> Option A

4. Quick Check:

   Appending and exporting PATH is correct [OK]

Hint: Appending PATH then exporting is standard practice [OK]

Common Mistakes:

• Thinking export must be on same line as assignment
• Confusing append with overwrite
• Assuming order of PATH parts always matters

5. You want to create a script that sets a temporary environment variable TEMP_VAR only for a single command execution, without affecting the shell's environment afterwards. Which command correctly does this?

hard

A. TEMP_VAR=value command

B. export TEMP_VAR=value; command

C. set TEMP_VAR=value command

D. command; export TEMP_VAR=value

Solution

1. Step 1: Understand temporary environment variables for one command

   Setting a variable before a command like TEMP_VAR=value command runs the command with that variable set only for its execution.

2. Step 2: Evaluate each option

   export TEMP_VAR=value; command exports variable globally; set TEMP_VAR=value command uses invalid syntax; command; export TEMP_VAR=value sets variable after command runs.

3. Final Answer:

   TEMP_VAR=value command -> Option A

4. Quick Check:

   Prefix variable before command for temporary env [OK]

Hint: Put variable before command to set it temporarily [OK]

Common Mistakes:

• Using export which affects shell permanently
• Trying to set variable after command runs
• Using incorrect syntax like 'set' for env variables