Unsetting variables (unset) in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to unset the variable named my_var.

Bash Scripting

unset [1]

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

Amy_var

Bunset

Cvar

Dvariable

Attempts:

3 left

💡 Hint

Common Mistakes

Using the word 'unset' as the variable name.

Using a wrong variable name like 'var' or 'variable'.

The unset command removes the variable named my_var from the environment.

2fill in blank

medium

Complete the code to unset the variable temp in a script.

Bash Scripting

unset [1]

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

Atemps

Btemporary

Ctmp

Dtemp

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to unset a variable with a similar but incorrect name.

Using a plural or extended form of the variable name.

The unset command removes the variable named exactly temp.

3fill in blank

hard

Fix the error in the code to properly unset the variable data.

Bash Scripting

unset [1]

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

A*data

B$data

Cdata

D&data

Attempts:

3 left

💡 Hint

Common Mistakes

Using $ before the variable name in unset.

Using special characters like * or & before the variable name.

When unsetting a variable, do not use the dollar sign. Just write the variable name.

4fill in blank

hard

Fill both blanks to unset the variable count and then print its value.

Bash Scripting

unset [1]
echo $[2]

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

Acount

Cvalue

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in unset and echo.

Trying to unset with a wrong variable name.

First, unset the variable named count. Then, echo its value using $count.

5fill in blank

hard

Fill all three blanks to unset variables a and b, then print a.

Bash Scripting

unset [1] [2]
echo $[3]

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

Aa

Bb

Dc

Attempts:

3 left

💡 Hint

Common Mistakes

Unsetting only one variable instead of two.

Echoing a variable not unset or not declared.

You can unset multiple variables by listing them. Then echo the variable a.

Practice

1. What does the unset command do in a bash script?

easy

A. It removes a variable from the environment, making it undefined.

B. It sets a variable to an empty string but keeps it defined.

C. It prints the value of a variable to the terminal.

D. It creates a new variable with a default value.

Solution

1. Step 1: Understand the purpose of unset

   The unset command removes a variable completely from the shell environment, so it no longer exists.

2. Step 2: Compare with other options

   Setting a variable to empty string keeps it defined, printing shows value, creating new variable is unrelated.

3. Final Answer:

   It removes a variable from the environment, making it undefined. -> Option A

4. Quick Check:

   unset removes variable = A [OK]

Hint: Unset deletes variable completely, not just empties it [OK]

Common Mistakes:

• Thinking unset sets variable to empty string
• Confusing unset with echo or print commands
• Assuming unset creates variables

2. Which of the following is the correct syntax to unset a variable named myVar in bash?

easy

A. unset =myVar

B. unset myVar

C. unset(myVar)

D. unset:myVar

Solution

1. Step 1: Recall the syntax of unset command

   The correct syntax is simply unset variable_name without any symbols or parentheses.

2. Step 2: Check each option

   unset myVar matches the correct syntax. Options B, C, and D use invalid characters or formats.

3. Final Answer:

   unset myVar -> Option B

4. Quick Check:

   Correct unset syntax = A [OK]

Hint: Use 'unset variableName' without symbols or parentheses [OK]

Common Mistakes:

• Adding equal signs or parentheses
• Using colons or other separators
• Confusing unset syntax with function calls

3. What will be the output of this bash script?

myVar="Hello"
echo $myVar
unset myVar
echo $myVar

medium

A. Hello

B. Hello
Hello

C. olleH

D. Error: variable not found

Solution

1. Step 1: Analyze the first echo command

   Variable myVar is set to "Hello", so echo $myVar prints "Hello".

2. Step 2: Understand effect of unset and second echo

   After unset myVar, the variable is removed. The second echo $myVar prints nothing (empty line).

3. Final Answer:

   Hello -> Option A

4. Quick Check:

   Unset removes variable, so second echo is empty [OK]

Hint: Unset clears variable, so echo after unset prints nothing [OK]

Common Mistakes:

• Expecting echo to print old value after unset
• Thinking unset causes error on echo
• Confusing unset with setting empty string

4. Identify the error in this script snippet:

unset $myVar

medium

A. No error; script works fine.

B. unset command requires quotes around variable name.

C. Variable name must be uppercase for unset.

D. Using $ before variable name in unset causes error.

Solution

1. Step 1: Understand how unset expects variable names

   The unset command expects the variable name without the $ sign, which is used for expansion.

2. Step 2: Analyze the given command

   Using unset $myVar expands $myVar to its value, causing unset to try to remove a variable named as that value, which is incorrect.

3. Final Answer:

   Using $ before variable name in unset causes error. -> Option D

4. Quick Check:

   unset needs variable name, no $ [OK]

Hint: Never use $ with variable name in unset command [OK]

Common Mistakes:

• Adding $ before variable name in unset
• Quoting variable name unnecessarily
• Assuming variable case matters for unset

5. You have a script that sets multiple variables:

var1="one"
var2="two"
var3="three"

You want to unset only variables that start with var and end with an odd number (1 or 3). Which command correctly unsets these variables?

hard

A. unset var1 var2 var3

B. unset var2 var3

C. unset var1 var3

D. unset var2

Solution

1. Step 1: Identify variables starting with 'var' and ending with odd numbers

   Variables are var1, var2, var3. var1 ends with 1 (odd), var3 ends with 3 (odd), var2 ends with 2 (even).

2. Step 2: Select variables to unset

   Only var1 and var3 match the pattern, so the command should unset these two.

3. Final Answer:

   unset var1 var3 -> Option C

4. Quick Check:

   Unset only odd-ending vars = A [OK]

Hint: Unset only variables matching pattern explicitly [OK]

Common Mistakes:

• Unsetting all variables instead of selective ones
• Confusing odd and even numbers
• Using unset with variable values instead of names