for loop (list-based) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a simple list-based for loop

What is the output of this Bash script?

Bash Scripting

for item in apple banana cherry; do
  echo $item
 done

A apple banana cherry

B

item
item
item

C

apple
banana
cherry

D Syntax error

💡 Hint

Remember that the loop runs once for each item in the list and echo prints each item on a new line.

The for loop iterates over each word in the list and echoes it. Each echo outputs on a new line.

💻 Command Output

intermediate

Counting items in a list with a for loop

What is the value of the variable count after running this script?

Bash Scripting

count=0
for word in one two three four; do
  count=$((count + 1))
done
echo $count

A Syntax error

B 4

C 1

D 0

💡 Hint

The loop increments count once for each word in the list.

The loop runs 4 times, increasing count by 1 each time, so count ends at 4.

💻 Command Output

advanced

Output of nested for loops with lists

What is the output of this Bash script?

Bash Scripting

for i in 1 2; do
  for j in a b; do
    echo "$i$j"
  done
done

A

1a
1b
2a
2b

B

1 2
a b

C 1a 1b 2a 2b

D Syntax error

💡 Hint

The outer loop runs twice, and for each iteration the inner loop runs twice.

The script prints each combination of i and j on its own line: 1a, 1b, 2a, 2b.

💻 Command Output

advanced

Effect of quotes in list-based for loop

What is the output of this Bash script?

Bash Scripting

for item in "one two" three; do
  echo "$item"
done

A

"one two"
three

B

one
two
three

C Syntax error

D

one two
three

💡 Hint

Quotes group words together as a single item in the list.

The first item is the string 'one two' as one item, then 'three' as the second item.

💻 Command Output

expert

Output of for loop with command substitution and word splitting

What is the output of this Bash script?

Bash Scripting

for file in $(echo "file1.txt file2.txt"); do
  echo "$file"
done

A

file1.txt
file2.txt

B "file1.txt file2.txt"

C file1.txt file2.txt

D Syntax error

💡 Hint

Command substitution outputs a string that is split into words for the loop.

The command substitution outputs two words separated by space, so the loop runs twice.

Practice

1. What does the following Bash code do?

for item in apple banana cherry; do echo $item; done

easy

A. Prints each fruit name on a new line

B. Prints all fruit names on the same line

C. Creates a list of fruits without printing

D. Causes a syntax error

Solution

1. Step 1: Understand the for loop structure

   The loop goes through each word in the list: apple, banana, cherry.

2. Step 2: Check the command inside the loop

   It prints each item using echo, so each fruit name appears on its own line.

3. Final Answer:

   Prints each fruit name on a new line -> Option A

4. Quick Check:

   Loop prints each item line by line = C [OK]

Hint: For loops print each list item one by one [OK]

Common Mistakes:

• Thinking echo prints all items on one line
• Confusing list iteration with variable assignment
• Missing the do/done keywords

2. Which of these is the correct syntax for a Bash for loop over a list of words?

easy

A. loop item in apple banana cherry: echo $item

B. for (item in apple banana cherry) { echo $item }

C. for item in apple banana cherry; do echo $item; done

D. foreach item in apple banana cherry; echo $item; end

Solution

1. Step 1: Identify valid Bash for loop syntax

   Bash uses: for variable in list; do commands; done

2. Step 2: Compare options

   Only for item in apple banana cherry; do echo $item; done matches Bash syntax exactly; others use syntax from other languages or invalid forms.

3. Final Answer:

   for item in apple banana cherry; do echo $item; done -> Option C

4. Quick Check:

   Bash for loop syntax = D [OK]

Hint: Bash loops use 'for var in list; do ...; done' [OK]

Common Mistakes:

• Using parentheses or braces like other languages
• Using foreach or loop keywords not in Bash
• Omitting do or done keywords

3. What is the output of this script?

for word in one two three; do echo "$word"; done

medium

A. one
two
three (each on its own line)

B. one\ntwo\nthree

C. one
two
three

D. one two three

Solution

1. Step 1: Understand the loop iteration

   The loop runs three times, each time echoing one word: one, two, three.

2. Step 2: Understand echo output with quotes

   Quotes preserve spaces but echo prints each word on a new line by default.

3. Final Answer:

   one two three (each on its own line) -> Option A

4. Quick Check:

   Echo prints each item on separate lines = A [OK]

Hint: Echo prints each loop item on its own line by default [OK]

Common Mistakes:

• Thinking echo prints all items on one line
• Confusing literal \n with newline
• Ignoring quotes effect on output

4. Find the error in this Bash script:

for item apple banana cherry; do echo $item; done

medium

A. Missing semicolon after 'banana'

B. Variable name 'item' is invalid

C. Incorrect use of quotes around list items

D. Missing 'in' keyword after 'for item'

Solution

1. Step 1: Check for loop syntax

   Bash requires 'for variable in list; do ...; done'. The 'in' keyword is missing here.

2. Step 2: Identify the error cause

   Without 'in', Bash cannot parse the list, causing a syntax error.

3. Final Answer:

   Missing 'in' keyword after 'for item' -> Option D

4. Quick Check:

   For loop needs 'in' keyword = B [OK]

Hint: Always include 'in' after variable in for loops [OK]

Common Mistakes:

• Forgetting the 'in' keyword
• Adding unnecessary semicolons inside list
• Misnaming variables with invalid characters

5. You want to print only the fruits that start with the letter 'b' from this list:

fruits="apple banana cherry blueberry"
for fruit in $fruits; do
  # Fill condition here
  echo "$fruit"
done

Which condition inside the loop correctly filters fruits starting with 'b'?

hard

A. if [ $fruit = 'b' ]; then

B. if [[ $fruit == b* ]]; then

C. if [[ $fruit =~ b* ]]; then

D. if [ $fruit == 'b*' ]; then

Solution

1. Step 1: Understand string pattern matching in Bash

   Double brackets [[ ]] support pattern matching with == and wildcards like '*'.

2. Step 2: Check each condition

   A uses [[ $fruit == b* ]] which matches strings starting with 'b'. B uses single brackets for exact 'b' match. C uses [[ $fruit =~ b* ]]; b* regex matches zero or more 'b's (including none), so every string. D uses single brackets which don't support patterns or ==.

3. Final Answer:

   if [[ $fruit == b* ]]; then -> Option B

4. Quick Check:

   Use [[ var == pattern* ]] for prefix match = A [OK]

Hint: Use [[ var == prefix* ]] to match string start in Bash [OK]

Common Mistakes:

• Using single brackets with wildcard patterns
• Confusing regex =~ with == operator
• Comparing to exact string 'b' instead of prefix