for loop with range ({1..10}) in Bash Scripting - Mini Project: Build & Apply

Counting Numbers with a Bash For Loop

📖 Scenario: Imagine you want to count from 1 to 10 using a simple script. This is like counting steps as you walk up a staircase.

🎯 Goal: You will write a Bash script that uses a for loop with a range {1..10} to print numbers from 1 to 10, one number per line.

📋 What You'll Learn

Create a Bash script variable to hold a greeting message.

Create a variable to hold the range of numbers from 1 to 10.

Use a for loop with the range {1..10} to print each number.

Print the greeting message before the numbers.

💡 Why This Matters

🌍 Real World

Counting or looping through numbers is common in scripts that automate tasks like backups, monitoring, or batch processing files.

💼 Career

Knowing how to use loops and ranges in Bash is a basic skill for system administrators, DevOps engineers, and anyone automating tasks on Linux or Unix systems.

1

Create a greeting message variable

Create a Bash variable called greeting and set it to the exact text "Counting from 1 to 10:".

Bash Scripting

# Create a variable called greeting with the text "Counting from 1 to 10:"
# Your code here

Hint

Use variable_name="text" to create a string variable in Bash.

2

Create a variable for the number range

Create a Bash variable called numbers and set it to the range {1..10} exactly as numbers="{1..10}".

Bash Scripting

greeting="Counting from 1 to 10:"
# Create a variable called numbers with the value "{1..10}"
# Your code here

Hint

Remember to put the range in quotes to assign it as a string.

3

Use a for loop with the range to print numbers

Write a for loop using for i in {1..10} to print each number i on its own line using echo.

Bash Scripting

greeting="Counting from 1 to 10:"
numbers="{1..10}"
# Use a for loop with 'for i in {1..10}' to print each number
# Your code here

Hint

The loop starts with for i in {1..10}, then do, then the commands, and ends with done.

4

Print the greeting and the numbers

Add a line to print the greeting variable before the loop using echo "$greeting".

Bash Scripting

greeting="Counting from 1 to 10:"
numbers="{1..10}"
# Print the greeting message
# Your code here
for i in {1..10}
do
  echo "$i"
done

Hint

Use echo "$greeting" before the loop to show the message.

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