if-then-else in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the variable num is equal to 10.

Bash Scripting

if [ "$num" [1] 10 ]; then
  echo "Number is ten"
fi

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

A==

B=

C!=

D-eq

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' or '==' which are for strings, not integers.

Forgetting spaces around brackets.

In bash, to compare integers inside [ ], use -eq for equality.

2fill in blank

medium

Complete the code to print "Positive" if the variable num is greater than zero.

Bash Scripting

if [ "$num" [1] 0 ]; then
  echo "Positive"
fi

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

A-gt

B-lt

C-eq

D-ne

Attempts:

3 left

💡 Hint

Common Mistakes

Using string comparison operators instead of numeric ones.

Using -lt which means less than.

Use -gt to check if a number is greater than another in bash.

3fill in blank

hard

Fix the error in the if statement to correctly check if word equals "hello".

Bash Scripting

if [[ $word [1] "hello" ]]; then
  echo "Greeting detected"
fi

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

A-eq

B=

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using single equals = inside [[ ]] which is less common and can cause issues.

Using numeric operators like -eq for strings.

Inside double brackets [[ ]], use == for string comparison.

4fill in blank

hard

Fill both blanks to complete the if-else statement that prints "Even" if num is divisible by 2, else prints "Odd".

Bash Scripting

if [ $((num [1] 2)) [2] 0 ]; then
  echo "Even"
else
  echo "Odd"
fi

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

A%

B-eq

C-ne

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using division / instead of modulus %.

Using -ne instead of -eq.

Use modulus operator % to get remainder and -eq to check if it equals zero.

5fill in blank

hard

Fill all three blanks to create a nested if-else that prints "Positive", "Zero", or "Negative" based on num.

Bash Scripting

if [ $num [1] 0 ]; then
  echo "Positive"
elif [ $num [2] 0 ]; then
  echo "Zero"
else
  echo "Negative"
fi

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

A-gt

B-eq

C-lt

D-ne

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of conditions.

Using string comparison operators instead of numeric ones.

Use -gt for greater than zero, -eq for zero, and -lt for less than zero.

Practice

1. What does the if-then-else structure do in a bash script?

easy

A. It comments out lines in the script.

B. It repeats a set of commands multiple times.

C. It defines a function to reuse code.

D. It lets the script choose between two paths based on a condition.

Solution

1. Step 1: Understand the purpose of if-then-else

   The if-then-else structure checks a condition and runs code based on whether the condition is true or false.

2. Step 2: Compare with other options

   Repeating commands is done with loops, functions reuse code, and comments do not execute code.

3. Final Answer:

   It lets the script choose between two paths based on a condition. -> Option D

4. Quick Check:

   if-then-else = choose path [OK]

Hint: If you see a condition, it's likely if-then-else [OK]

Common Mistakes:

• Confusing if-then-else with loops
• Thinking if-then-else defines functions
• Mixing comments with control flow

2. Which of the following is the correct syntax to start an if statement in bash?

easy

A. if [ condition ]; then

B. if { condition } then

C. if(condition) then

D. if condition then

Solution

1. Step 1: Recall bash if syntax

   Bash requires spaces around brackets and a semicolon before then: if [ condition ]; then.

2. Step 2: Check other options

   if(condition) then misses spaces and semicolon, B uses braces incorrectly, D misses brackets and semicolon.

3. Final Answer:

   if [ condition ]; then -> Option A

4. Quick Check:

   Spaces and semicolon needed [OK]

Hint: Remember spaces around [ ] and semicolon before then [OK]

Common Mistakes:

• No spaces around brackets
• Missing semicolon before then
• Using parentheses or braces incorrectly

3. What will be the output of this script?

#!/bin/bash
x=5
if [ $x -gt 3 ]; then
  echo "Greater"
else
  echo "Smaller"
fi

medium

A. No output

B. Smaller

C. Greater

D. Syntax Error

Solution

1. Step 1: Evaluate the condition

   The condition checks if x (5) is greater than 3, which is true.

2. Step 2: Determine which branch runs

   Since condition is true, the script prints "Greater".

3. Final Answer:

   Greater -> Option C

4. Quick Check:

   5 > 3 = Greater [OK]

Hint: Check numeric comparison carefully [OK]

Common Mistakes:

• Confusing -gt with -lt
• Missing spaces causing syntax errors
• Assuming else runs when condition is true

4. Find the error in this script:

#!/bin/bash
if [ $num -eq 10 ]
  echo "Ten"
else
  echo "Not Ten"
fi

medium

A. Missing then after condition

B. Wrong comparison operator

C. Missing fi at the end

D. No error

Solution

1. Step 1: Check if statement syntax

   The if condition must be followed by then keyword to start the true block.

2. Step 2: Identify missing part

   The script misses then after the condition line.

3. Final Answer:

   Missing then after condition -> Option A

4. Quick Check:

   if needs then [OK]

Hint: Always put then after condition in if [ ] [OK]

Common Mistakes:

• Forgetting then keyword
• Using wrong comparison operators
• Missing fi to close if

5. You want a script that prints "Even" if a number is even, and "Odd" if it is odd. Which script correctly uses if-then-else to do this?

num=4
# Choose correct script

hard

A. if [ $num % 2 -eq 0 ]; then
echo "Even"
else
echo "Odd"
fi

B. if (( num % 2 == 0 )); then
echo "Even"
else
echo "Odd"
fi

C. if [ $num % 2 == 0 ]; then
echo "Even"
else
echo "Odd"
fi

D. if [ $num / 2 -eq 0 ]; then
echo "Even"
else
echo "Odd"
fi

Solution

1. Step 1: Understand arithmetic evaluation in bash

   Using double parentheses (( )) allows arithmetic expressions and comparisons directly.

2. Step 2: Check each option

   if [ $num % 2 -eq 0 ]; then echo "Even" else echo "Odd" fi uses % inside [ ] without arithmetic evaluation. if [ $num % 2 == 0 ]; then echo "Even" else echo "Odd" fi uses % inside [ ] without arithmetic evaluation. if [ $num / 2 -eq 0 ]; then echo "Even" else echo "Odd" fi uses / instead of % for modulus. if (( num % 2 == 0 )); then echo "Even" else echo "Odd" fi correctly uses (( )) with modulus and comparison.

3. Final Answer:

   if (( num % 2 == 0 )); then echo "Even" else echo "Odd" fi -> Option B

4. Quick Check:

   Use (( )) for arithmetic if [OK]

Hint: Use (( )) for math conditions in bash [OK]

Common Mistakes:

• Using [ ] with arithmetic operators incorrectly
• Confusing / with % for modulus
• Missing then keyword