export command in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the export command do in Linux?

The export command sets environment variables so that they are available to child processes started from the current shell.

beginner

How do you make a variable named MY_VAR available to other programs using export?

You write: export MY_VAR=value. This sets MY_VAR and exports it to child processes.

beginner

What happens if you set a variable without export?

The variable exists only in the current shell and is not passed to child processes or other programs.

beginner

How can you see all exported environment variables in your current shell?

Use the command export -p or printenv to list all exported environment variables.

intermediate

Can you export a variable that was already set without reassigning it?

Yes, just run export VARIABLE_NAME to export an existing variable without changing its value.

What does the export command do?

A Deletes a variable

B Lists all files in a directory

C Changes the shell prompt

D Makes a variable available to child processes

The export command marks variables to be passed to child processes.

Which command exports a variable named PATH with a new value?

A env PATH=/usr/bin

B export PATH=/usr/bin

C PATH=/usr/bin

D set PATH=/usr/bin

Only export PATH=/usr/bin sets and exports the variable.

If you set a variable without export, what happens?

A It is only available in the current shell

B It is deleted immediately

C It is available to child processes

D It becomes a system variable

Variables without export stay local to the current shell.

How do you list all exported variables?

A export -p

B lsenv

C showenv

D envlist

The command export -p lists all exported variables.

Can you export a variable without assigning a new value?

A Only if the variable is empty

B No, you must assign a value

C Yes, just use <code>export VARIABLE_NAME</code>

D Only in root user

You can export an existing variable by just running export VARIABLE_NAME.

Explain in your own words what the export command does and why it is useful.

Think about how programs get information from the shell.

Describe the difference between setting a variable with and without export.

Consider where the variable can be seen or used.

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