for loop with range ({1..10}) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a simple for loop with brace expansion

What is the output of this Bash script?

for i in {1..5}; do echo $i; done

Bash Scripting

for i in {1..5}; do echo $i; done

A

1
2
3
4
5

B

0
1
2
3
4
5

C

1
2
3
4

D 1 2 3 4 5

💡 Hint

Brace expansion generates a sequence of numbers separated by spaces.

The brace expansion {1..5} generates numbers 1 to 5. The loop echoes each number on its own line.

💻 Command Output

intermediate

Behavior of for loop with variable expansion inside range

What will this script output?

start=3
end=7
for i in {$start..$end}; do echo $i; done

Bash Scripting

start=3
end=7
for i in {$start..$end}; do echo $i; done

A

3
4
5
6
7

B {3..7}

C 3 4 5 6 7

D Syntax error

💡 Hint

Brace expansion happens before variable expansion in Bash.

Brace expansion occurs before variable expansion, so {$start..$end} is not expanded as a numeric range; it becomes the literal string '{3..7}' after variable expansion.

📝 Syntax

advanced

Correct syntax for a for loop counting down with brace expansion

Which option correctly counts down from 10 to 1 using brace expansion in Bash?

A for i in {1..10..-1}; do echo $i; done

B for i in {10..1}; do echo $i; done

C for i in {10..1..1}; do echo $i; done

D for i in {10..1..-1}; do echo $i; done

💡 Hint

Brace expansion supports a step value for counting down.

The syntax {start..end..step} allows counting down with a negative step. {10..1..-1} counts from 10 down to 1.

🚀 Application

advanced

Using a for loop with brace expansion to create files

You want to create 5 empty files named file1.txt to file5.txt using a Bash for loop with brace expansion. Which command will do this?

A for i in {1..5}; do echo file$i.txt; done

B touch file{1..5}.txt

C for i in {1..5}; do touch file$i.txt; done

D for i in {1..5}; touch file$i.txt

💡 Hint

Use a loop to run the touch command multiple times with different file names.

Option C loops from 1 to 5 and creates each file with touch. Option C expands to 'touch file1.txt file2.txt file3.txt file4.txt file5.txt' creating all files without a loop; the task requires a for loop.

🔧 Debug

expert

Why does this for loop not print numbers 1 to 10?

Consider this script:

for i in {1..10} do
echo $i
done

Why does it fail to print numbers 1 to 10?

Bash Scripting

for i in {1..10} do
echo $i
done

A Missing semicolon or newline after {1..10} causes syntax error

B Variable $i is not defined before the loop

C Brace expansion does not work with for loops

D The loop variable must be declared with 'declare' before use

💡 Hint

Check the syntax of the for loop header carefully.

In Bash, the for loop header must end with a semicolon or newline before 'do'. Missing this causes a syntax error.

Practice

1. What does the following Bash loop do?
for i in {1..5}; do echo $i; done

easy

A. Causes a syntax error

B. Prints numbers 1 to 5, each on a new line

C. Prints numbers 0 to 4, each on a new line

D. Prints the string '{1..5}' once

Solution

1. Step 1: Understand the loop range syntax

   The loop uses {1..5}, which expands to numbers 1, 2, 3, 4, 5.

2. Step 2: Check the loop body output

   Each iteration prints the current number, so numbers 1 to 5 print on separate lines.

3. Final Answer:

   Prints numbers 1 to 5, each on a new line -> Option B

4. Quick Check:

   Range {1..5} loops from 1 to 5 [OK]

Hint: Curly braces {1..5} generate numbers 1 to 5 [OK]

Common Mistakes:

• Thinking {1..5} is a string, not a range
• Confusing range start and end values
• Expecting zero-based counting

2. Which of the following is the correct syntax to loop from 1 to 10 in Bash using brace expansion?

easy

A. for i in {1..10}; do echo $i; done

B. for i in [1..10]; do echo $i; done

C. for i in (1..10); do echo $i; done

D. for i in <1..10>; do echo $i; done

Solution

1. Step 1: Identify correct brace expansion syntax

   Bash uses curly braces {start..end} for ranges, so {1..10} is correct.

2. Step 2: Check other options for syntax errors

   Parentheses, square brackets, and angle brackets are invalid for this purpose in Bash loops.

3. Final Answer:

   for i in {1..10}; do echo $i; done -> Option A

4. Quick Check:

   Brace expansion uses curly braces {..} [OK]

Hint: Use curly braces {start..end} for ranges in Bash loops [OK]

Common Mistakes:

• Using parentheses or brackets instead of braces
• Missing the 'in' keyword
• Forgetting to close the loop with 'done'

3. What is the output of this script?

for i in {3..6}; do echo $((i * 2)); done

medium

A. 2 4 6 8

B. 3 4 5 6

C. 6
8
10
12

D. Error: invalid arithmetic

Solution

1. Step 1: Identify loop values

   The loop variable i takes values 3, 4, 5, 6 from {3..6}.

2. Step 2: Calculate output for each iteration

   Each iteration prints i * 2: 3*2=6, 4*2=8, 5*2=10, 6*2=12.

3. Final Answer:

   6 8 10 12 -> Option C

4. Quick Check:

   Multiply each i by 2 [OK]

Hint: Multiply loop variable inside $(( )) for arithmetic [OK]

Common Mistakes:

• Confusing loop values with output
• Using single parentheses instead of $(( ))
• Expecting space-separated output on one line

4. Find the error in this Bash loop:

for i in {1..5} do
echo $i
done

medium

A. Variable $i is not defined

B. Loop body must be on the same line as for

C. Brace expansion syntax is wrong

D. Missing semicolon or newline after {1..5}

Solution

1. Step 1: Check for syntax correctness in loop header

   The for loop header must end with a semicolon or newline before 'do'. Here, 'do' follows directly after {1..5} without either, causing a syntax error.

2. Step 2: Verify other parts

   Variable $i is defined by the loop, brace syntax is correct, and loop body can be on next lines.

3. Final Answer:

   Missing semicolon or newline after {1..5} -> Option D

4. Quick Check:

   Loop header must end properly before 'do' [OK]

Hint: Put semicolon or newline before 'do' in for loops [OK]

Common Mistakes:

• Omitting semicolon or newline before 'do'
• Misunderstanding brace expansion syntax
• Thinking loop body must be on same line

5. You want to print only even numbers from 2 to 10 using a Bash for loop with brace expansion. Which script achieves this?

hard

A. for i in {2..10..2}; do echo $i; done

B. for i in {1..10}; do if [ $i % 2 == 0 ]; then echo $i; fi; done

C. for i in {2..10}; do echo $((i*2)); done

D. for i in {2..10..3}; do echo $i; done

Solution

1. Step 1: Understand brace expansion with step

   Brace expansion supports {start..end..step}, so {2..10..2} generates even numbers 2,4,6,8,10.

2. Step 2: Check other options

   B uses [ ] test which performs string comparison, not arithmetic modulo, so never prints evens; C multiplies numbers incorrectly to 4,6,8,10,12,14,16,18,20; D steps by 3, not 2.

3. Final Answer:

   for i in {2..10..2}; do echo $i; done -> Option A

4. Quick Check:

   Use {start..end..step} for stepped ranges [OK]

Hint: Use {start..end..step} to loop with steps in Bash [OK]

Common Mistakes:

• Not using step in brace expansion
• Multiplying loop variable instead of stepping
• Using wrong step size