export command in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the export command?

You run the following commands in a Linux shell:

MYVAR=hello
export MYVAR
export

What will be part of the output when you run export?

Linux CLI

MYVAR=hello
export MYVAR
export

A Only the variable MYVAR=hello is shown

B A list of all exported environment variables including MYVAR=hello

C No output is shown

D An error message saying 'export: command not found'

💡 Hint

The export command without arguments lists all exported variables.

The export command without arguments prints all environment variables that are exported. Since MYVAR was exported, it will appear in the list with its value.

💻 Command Output

intermediate

What happens when you export a variable with spaces?

Consider the commands:

export MYVAR=hello world
export MYVAR

What will happen when you run these commands in a Linux shell?

Linux CLI

export MYVAR=hello world
export MYVAR

A MYVAR is unset

B MYVAR is set to 'hello world' correctly

C MYVAR is set to 'hello' and 'world' is treated as a separate command

D Syntax error because of the space in the value without quotes

💡 Hint

Spaces in variable values need quotes.

Without quotes, the shell treats 'world' as a separate command or argument, causing a syntax error.

🔧 Debug

advanced

Why does this export command not set the variable in the parent shell?

You run this command in your shell:

export MYVAR=hello

Then in a new terminal, you run:

echo $MYVAR

But it prints nothing. Why?

Linux CLI

export MYVAR=hello
# In a new terminal:
echo $MYVAR

A Because echo command is wrong

B Because MYVAR was not set correctly

C Because export only affects the current shell and its child processes, not new terminals

D Because export clears variables after the command finishes

💡 Hint

Think about how environment variables are inherited.

Environment variables set with export exist only in the current shell session and its children. New terminals start new shells without those variables.

🧠 Conceptual

advanced

What is the effect of 'export -n VAR' in Linux shell?

You have a variable VAR exported. What does the command export -n VAR do?

Linux CLI

export VAR=hello
export -n VAR

A It removes the export attribute, so VAR is no longer exported to child processes

B It sets VAR to an empty string

C It exports VAR with a new value '-n VAR'

D It causes a syntax error

💡 Hint

The -n option removes export status.

The export -n command removes the export attribute from the variable, so it remains in the shell but is not passed to child processes.

🚀 Application

expert

How to export multiple variables in one command correctly?

You want to export two variables VAR1 and VAR2 with values 'foo' and 'bar' in one command. Which command does this correctly?

A export VAR1=foo VAR2=bar

B export VAR1=foo; export VAR2=bar

C export VAR1=foo, VAR2=bar

D export VAR1=foo && VAR2=bar

💡 Hint

Multiple variables can be exported in one export command separated by spaces.

The export command accepts multiple variable assignments separated by spaces. Commas or && are not valid separators here.

Practice

1. What does the export command do in a Linux shell?

easy

A. Makes a shell variable available to child processes

B. Deletes a shell variable permanently

C. Lists all files in the current directory

D. Changes the current directory

Solution

1. Step 1: Understand shell variables and environment

   Shell variables exist only in the current shell session unless exported.

2. Step 2: Role of export

   The export command marks a variable to be passed to child processes as environment variables.

3. Final Answer:

   Makes a shell variable available to child processes -> Option A

4. Quick Check:

   export = share variable with child processes [OK]

Hint: Export shares variables with child processes [OK]

Common Mistakes:

• Thinking export deletes variables
• Confusing export with file commands
• Assuming export changes directories

2. Which of the following is the correct syntax to export a variable named PATH with value /usr/local/bin?

easy

A. export =PATH /usr/local/bin

B. export PATH=/usr/local/bin

C. export PATH : /usr/local/bin

D. export PATH == /usr/local/bin

Solution

1. Step 1: Recall export syntax

   The correct syntax is export VARIABLE=VALUE without spaces around the equal sign.

2. Step 2: Check each option

   export PATH=/usr/local/bin matches the correct syntax. Others have invalid characters or spaces.

3. Final Answer:

   export PATH=/usr/local/bin -> Option B

4. Quick Check:

   export VAR=VALUE no spaces [OK]

Hint: No spaces around = in export syntax [OK]

Common Mistakes:

• Adding spaces around equal sign
• Using wrong symbols like : or ==
• Placing export after assignment

3. What will be the output of the following commands?

MYVAR="hello"
echo $MYVAR
export MYVAR
bash -c 'echo $MYVAR'

medium

A. \n\n

B. hello\n

C. \nhello

D. hello\nhello

Solution

1. Step 1: Understand variable assignment and export

   First, MYVAR is set to "hello" and printed, so first echo outputs "hello". Then MYVAR is exported.

2. Step 2: Child shell access

   The bash -c 'echo $MYVAR' runs a new shell which inherits exported variables, so it prints "hello" again.

3. Final Answer:

   hello hello -> Option D

4. Quick Check:

   Exported variable visible in child shell [OK]

Hint: Exported vars visible in child shells [OK]

Common Mistakes:

• Assuming unexported vars appear in child shells
• Confusing echo outputs with command prompts
• Ignoring export effect on subshells

4. Identify the error in this script snippet:

export MYVAR
MYVAR="world"
echo $MYVAR

medium

A. echo command is missing quotes

B. export command syntax is wrong

C. MYVAR is exported before assignment, so child shells get empty value

D. No error, script works fine

Solution

1. Step 1: Analyze export before assignment

   Exporting MYVAR before assigning means MYVAR is empty when exported.

2. Step 2: Effect on variable value

   Assigning MYVAR after export does not update the exported environment variable for child processes.

3. Final Answer:

   MYVAR is exported before assignment, so child shells get empty value -> Option C

4. Quick Check:

   Export before assignment exports empty value [OK]

Hint: Assign before export to share correct value [OK]

Common Mistakes:

• Exporting before assigning value
• Thinking export syntax is wrong
• Assuming echo needs quotes always

5. You want to set a variable CONFIG_PATH to /etc/config and ensure it is available to all scripts run from your current shell session and its children. Which sequence of commands achieves this correctly?

hard

A. CONFIG_PATH=/etc/config\nexport CONFIG_PATH

B. export CONFIG_PATH=/etc/config

C. export CONFIG_PATH\nCONFIG_PATH=/etc/config

D. CONFIG_PATH=/etc/config

Solution

1. Step 1: Assign variable before export

   Assigning CONFIG_PATH=/etc/config sets the value in the current shell.

2. Step 2: Export variable after assignment

   Running export CONFIG_PATH marks it for child processes with the assigned value.

3. Step 3: Check other options

   export CONFIG_PATH=/etc/config works but is less clear; export CONFIG_PATH\nCONFIG_PATH=/etc/config exports before assignment (wrong); CONFIG_PATH=/etc/config does not export.

4. Final Answer:

   CONFIG_PATH=/etc/config export CONFIG_PATH -> Option A

5. Quick Check:

   Assign then export to share variable [OK]

Hint: Assign first, then export to share variable [OK]

Common Mistakes:

• Exporting before assigning value
• Not exporting variable at all
• Assuming single export with assignment is always best