C-style for loop in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 1 to 5 using a C-style for loop in bash.

Bash Scripting

for (( i=1; i<=5; i[1] )); do
  echo $i
done

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

A+

B++

C--

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '--' which decreases the variable.

Using '+' or '*' which are not valid increment operators in this syntax.

The increment operator '++' increases the variable i by 1 each loop iteration.

2fill in blank

medium

Complete the code to print numbers from 10 down to 1 using a C-style for loop in bash.

Bash Scripting

for (( i=10; i[1]1; i-- )); do
  echo $i
done

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

A<

B<=

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '<=' which would not work for counting down.

Using '>' which would cause the loop to never run.

The loop continues while i is greater than or equal to 1.

3fill in blank

hard

Fix the error in the loop condition to print numbers from 0 to 4.

Bash Scripting

for (( i=0; i[1]5; i++ )); do
  echo $i
done

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

A<

B<=

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<=' causes the loop to print 5, which is not desired.

Using '>' or '>=' causes the loop to never run.

The loop should run while i is less than 5 to print 0 through 4.

4fill in blank

hard

Fill both blanks to create a loop that prints even numbers from 2 to 10.

Bash Scripting

for (( i=[1]; i[2]10; i+=2 )); do
  echo $i
done

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

A2

B1

C<=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Starting at 1 prints odd numbers.

Using '<' excludes 10 from the output.

Start at 2 and continue while i is less than or equal to 10, incrementing by 2.

5fill in blank

hard

Fill all three blanks to create a loop that prints numbers from 5 down to 0.

Bash Scripting

for (( [1]=5; [2][3]0; [1]-- )); do
  echo $[1]
done

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

Ai

Bj

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in initialization and condition.

Using '>' excludes 0 from the output.

Use variable i, loop while i is greater than or equal to 0, and decrement i each time.

Practice

1. What does the following C-style for loop do in bash?
for ((i=1; i<=3; i++)); do echo $i; done

easy

A. Prints numbers 1, 2, and 3 each on a new line

B. Prints numbers 0, 1, and 2 each on a new line

C. Prints numbers 1, 2, 3, and 4 each on a new line

D. Causes a syntax error

Solution

1. Step 1: Understand the loop initialization and condition

   The loop starts with i=1 and runs while i is less than or equal to 3.

2. Step 2: Analyze the increment and output

   Each iteration prints the current value of i, then increases i by 1 until i becomes 4 and stops.

3. Final Answer:

   Prints numbers 1, 2, and 3 each on a new line -> Option A

4. Quick Check:

   Loop from 1 to 3 prints 1, 2, 3 [OK]

Hint: Check start, end, and increment values carefully [OK]

Common Mistakes:

• Starting loop at 0 instead of 1
• Confusing <= with < in condition
• Forgetting to increment i

2. Which of the following is the correct syntax for a C-style for loop in bash?

easy

A. for (i=0; i<5; i++) do echo $i; done

B. for ((i=0; i<5; i++)); do echo $i; done

C. for [i=0; i<5; i++] do echo $i; done

D. for {i=0; i<5; i++} do echo $i; done

Solution

1. Step 1: Identify correct C-style for loop syntax in bash

   Bash requires double parentheses (( )) around the loop control with semicolons separating init, condition, and increment.

2. Step 2: Check each option

   for ((i=0; i<5; i++)); do echo $i; done uses double parentheses and semicolons correctly; others use incorrect brackets or missing parentheses.

3. Final Answer:

   for ((i=0; i<5; i++)); do echo $i; done -> Option B

4. Quick Check:

   Double parentheses and semicolons = correct syntax [OK]

Hint: Look for double parentheses and semicolons inside [OK]

Common Mistakes:

• Using single parentheses instead of double
• Using square or curly brackets
• Missing semicolons between parts

3. What is the output of this bash script?

for ((i=2; i<=6; i+=2)); do echo $i; done

medium

A. 2 3 4 5 6

B. Syntax error

C. 2 4 6 8

D. 2 4 6

Solution

1. Step 1: Understand loop initialization and increment

   The loop starts at i=2, runs while i is less than or equal to 6, and increments i by 2 each time.

2. Step 2: List values printed

   Values printed are 2, then 4, then 6. After 6, i becomes 8 which breaks the condition.

3. Final Answer:

   2 4 6 -> Option D

4. Quick Check:

   Increment by 2 from 2 to 6 prints 2,4,6 [OK]

Hint: Check increment step and loop condition carefully [OK]

Common Mistakes:

• Assuming increment is 1 by default
• Including numbers beyond the condition
• Confusing <= with <

4. Identify the error in this bash C-style for loop:

for ((i=0; i<5 i++)); do echo $i; done

medium

A. Missing semicolon between condition and increment

B. Using single parentheses instead of double

C. Incorrect variable name

D. Missing do keyword

Solution

1. Step 1: Check loop syntax parts

   The loop control must have three parts separated by semicolons: initialization, condition, and increment.

2. Step 2: Locate missing semicolon

   Between 'i<5' and 'i++' there is no semicolon, causing a syntax error.

3. Final Answer:

   Missing semicolon between condition and increment -> Option A

4. Quick Check:

   Semicolons separate parts in C-style for loops [OK]

Hint: Check for three semicolon-separated parts inside (( )) [OK]

Common Mistakes:

• Omitting semicolons between parts
• Using single parentheses
• Forgetting do keyword

5. You want to print all odd numbers from 1 to 9 using a C-style for loop in bash. Which script achieves this?

hard

A. for ((i=1; i<10; i++)); do if (( i % 2 == 0 )); then echo $i; fi; done

B. for ((i=0; i<10; i++)); do if (( i % 2 == 0 )); then echo $i; fi; done

C. for ((i=1; i<=9; i+=2)); do echo $i; done

D. All of the above

Solution

1. Step 1: Analyze for ((i=1; i<=9; i+=2)); do echo $i; done

   for ((i=1; i<=9; i+=2)); do echo $i; done starts at 1, increments by 2, prints 1,3,5,7,9 directly.

2. Step 2: Analyze options B and C

   Both loop with i++ and check if (( i % 2 == 0 )), which selects even numbers: B prints 0,2,4,6,8; C prints 2,4,6,8.

3. Final Answer:

   for ((i=1; i<=9; i+=2)); do echo $i; done -> Option C

4. Quick Check:

   Increment by 2 from 1 to <=9 prints odds 1-9 [OK]

Hint: Use increments or modulo checks to filter odd numbers [OK]

Common Mistakes:

• Using wrong increment step
• Starting from 0 without filtering
• Forgetting to check odd condition