Writing a shell script to loop and print out numbers 0-100 and if they are even or odd

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06-10-2024

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Looping Through Numbers: A Shell Script for Even and Odd Detection

Understanding how to manipulate numbers and identify their properties is fundamental in programming. This article will guide you through writing a simple shell script to loop through numbers from 0 to 100, determine if each number is even or odd, and print the results.

The Problem: We want to automate the process of identifying whether a range of numbers are even or odd, rather than manually checking each number.

The Solution: We can use a loop to iterate through the numbers, and a simple conditional statement to determine if each number is divisible by 2 (even) or not (odd).

The Shell Script

#!/bin/bash

for i in $(seq 0 100); do
  if (( i % 2 == 0 )); then
    echo "$i is even"
  else
    echo "$i is odd"
  fi
done

Explanation:

1. #!/bin/bash: This line indicates the script is to be run with the bash interpreter.
2. for i in $(seq 0 100); do: This line initiates a loop that iterates through numbers from 0 to 100.
   • seq 0 100 generates a sequence of numbers from 0 to 100.
   • for i in ... assigns each number from the sequence to the variable i for each iteration.
3. if (( i % 2 == 0 )); then: This line checks if the current number i is divisible by 2 with no remainder.
   • i % 2 calculates the remainder when i is divided by 2.
   • == 0 checks if the remainder is equal to 0, signifying an even number.
4. echo "$i is even": This line prints the number i and "is even" if the condition is true.
5. else: This line executes if the previous condition is false (meaning the number is odd).
6. echo "$i is odd": This line prints the number i and "is odd" if the condition is true.
7. fi: This line marks the end of the if statement.
8. done: This line marks the end of the for loop.

Running the Script:

1. Save the code in a file named even_odd.sh.
2. Make the script executable using chmod +x even_odd.sh.
3. Run the script by typing ./even_odd.sh.

Output: The script will print a list of numbers from 0 to 100, indicating whether each number is even or odd.

Key Insights

• Modulus operator (%): The modulus operator is crucial for determining even/odd numbers. It returns the remainder after a division operation.
• Shell Scripting: Shell scripts are powerful tools for automating repetitive tasks, such as this even/odd check.
• Conditional Statements (if and else): These statements allow us to execute different actions based on specific conditions.

Additional Resources:

• Bash scripting tutorials: https://www.gnu.org/software/bash/manual/bash.html, https://linuxhint.com/bash_scripting_tutorial/
• Shell script examples: https://www.shellscript.sh/

Conclusion:

By understanding the basics of looping and conditional statements in shell scripting, you can easily automate tasks like identifying even and odd numbers within a range. This script demonstrates a fundamental application of these concepts, which can be further expanded to tackle more complex problems.