Environment variables vs local variables in Bash Scripting - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a local variable named name with the value John.

Bash Scripting

name=[1]

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

AJohn

B'John'

C"John"

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes unnecessarily when not needed

Trying to export the variable when only local is needed

In bash, to assign a string value without spaces or special characters, you can simply write name=John. Quotes are optional here.

2fill in blank

medium

Complete the code to export a variable PATH with the value /usr/bin so it becomes an environment variable.

Bash Scripting

export PATH=[1]

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

APATH

B/usr/bin

C"/usr/bin"

D'/usr/bin'

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes causing errors if path contains spaces

Assigning without export so variable is local only

When exporting variables with paths or strings, it's good practice to use quotes to avoid issues with special characters or spaces.

3fill in blank

hard

Fix the error in the code to correctly print the value of the environment variable HOME.

Bash Scripting

echo [1]

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

A$HOME

BHOME

C${HOME}

Denv HOME

Attempts:

3 left

💡 Hint

Common Mistakes

Printing the variable name without $ so it prints the literal string

Using env HOME which is incorrect syntax

To print the value of an environment variable in bash, prefix it with $. So echo $HOME prints the home directory.

4fill in blank

hard

Fill both blanks to create a local variable var with value 5 and export it as an environment variable.

Bash Scripting

var=[1]
[2] var

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

A5

Bexport

Cset

Ddeclare

Attempts:

3 left

💡 Hint

Common Mistakes

Using set or declare instead of export

Putting quotes around the number 5

First assign the value 5 to var. Then use export var to make it an environment variable.

5fill in blank

hard

Fill all three blanks to create a local variable count with value 10, export it, and then print its value.

Bash Scripting

count=[1]
[2] count
[3] $count

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

A10

Bexport

Cecho

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using print instead of echo

Not exporting the variable before printing

Putting quotes around the number 10

Assign 10 to count, export it to make it an environment variable, then print its value using echo $count.

Practice

1. What is the main difference between an environment variable and a local variable in a Bash script?

easy

A. Local variables are available to child processes, environment variables are not.

B. Environment variables are available to child processes, local variables are not.

C. Environment variables can only be numbers, local variables can be strings.

D. Local variables are global, environment variables are only inside functions.

Solution

1. Step 1: Understand environment variables

   Environment variables are set with export and are inherited by child processes.

2. Step 2: Understand local variables

   Local variables exist only in the current shell or function and are not passed to child processes.

3. Final Answer:

   Environment variables are available to child processes, local variables are not. -> Option B

4. Quick Check:

   Environment = exported, local = not exported [OK]

Hint: Remember: export makes variables visible to child processes [OK]

Common Mistakes:

• Thinking local variables are inherited by child processes
• Confusing export with local keyword
• Assuming environment variables are only inside functions

2. Which of the following is the correct way to create a local variable inside a Bash function?

easy

A. VAR=value

B. export VAR=value

C. local VAR=value

D. setlocal VAR=value

Solution

1. Step 1: Identify local variable syntax in Bash functions

   Inside a function, the keyword local declares a variable limited to that function.

2. Step 2: Compare options

   export makes variables environment variables, setlocal is not a Bash command, and VAR=value without local is global or inherited.

3. Final Answer:

   local VAR=value -> Option C

4. Quick Check:

   Use local inside functions for local variables [OK]

Hint: Use 'local' keyword inside functions for local variables [OK]

Common Mistakes:

• Using export instead of local inside functions
• Assuming VAR=value inside function is local
• Using non-existent commands like setlocal

3. What will be the output of this script?

VAR=hello
function test_func() {
  local VAR=world
  echo $VAR
}
test_func
echo $VAR

medium

A. world
hello

B. hello
hello

C. world
world

D. hello
world

Solution

1. Step 1: Analyze variable inside function

   The function declares a local variable VAR with value 'world', so echo $VAR inside prints 'world'.

2. Step 2: Analyze variable outside function

   The global VAR remains 'hello', so echo $VAR after function call prints 'hello'.

3. Final Answer:

   world hello -> Option A

4. Quick Check:

   Local inside function, global outside [OK]

Hint: Local variables override global only inside functions [OK]

Common Mistakes:

• Assuming local variable changes global variable
• Confusing output order
• Ignoring local keyword effect

4. Identify the error in this script snippet:

export VAR=hello
function test() {
  VAR=world
  local VAR
  echo $VAR
}
test
echo $VAR

medium

A. local must be declared before assigning VAR inside function

B. export cannot be used outside functions

C. echo $VAR inside function will print empty

D. Function syntax is incorrect

Solution

1. Step 1: Understand local variable declaration order

   In Bash, local VAR must appear before assigning a value to VAR inside the function to make it local.

2. Step 2: Analyze the script behavior

   Here, VAR=world assigns to global VAR before local VAR is declared, so local VAR is empty and echo $VAR prints empty.

3. Final Answer:

   local must be declared before assigning VAR inside function -> Option A

4. Quick Check:

   Declare local before assignment inside functions [OK]

Hint: Declare local variables before assigning values inside functions [OK]

Common Mistakes:

• Assigning before declaring local causes unexpected behavior
• Thinking export is invalid outside functions
• Assuming function syntax is wrong

5. You want to write a Bash script that sets a variable PATH_VAR inside a function and have it available outside the function and in any child processes. Which is the correct approach?

hard

A. Inside the function, use export PATH_VAR=value after declaring local PATH_VAR.

B. Declare local PATH_VAR=value inside the function and then export PATH_VAR outside the function.

C. Use local PATH_VAR=value inside the function and do nothing else.

D. Assign PATH_VAR=value inside the function and then export PATH_VAR inside the function without local.

Solution

1. Step 1: Understand local vs exported variables

   Declaring a variable as local limits it to the function scope, so it won't be available outside or to child processes.

2. Step 2: Correct way to export variable from function

   Assign the variable without local inside the function, then use export PATH_VAR inside the function to make it environment variable accessible outside and to child processes.

3. Final Answer:

   Assign PATH_VAR=value inside the function and then export PATH_VAR inside the function without local. -> Option D

4. Quick Check:

   Export without local to share variable outside function [OK]

Hint: Don't use local if you want variable exported outside function [OK]

Common Mistakes:

• Using local and export together inside function
• Exporting variable only outside function after local declaration
• Assuming local variables can be exported