How to Create a Bash Script to Check if Numbers are Odd or Even in a File

Learn how to write a Bash script that checks whether the last column in a text file contains odd or even numbers, or if it’s not a number at all.
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How to Create a Bash Script to Check if Numbers are Odd or Even in a File

When working with data files, you may often need to determine if a number is odd or even. This can be particularly useful in scenarios such as data validation, reporting, or cleanup tasks in Linux environments. In this guide, we will guide you through the process of writing a Bash script that reads a text file and checks the last column of each row for odd and even numbers.

Problem Statement

Read the last column of each row.

Determine if the value is a number and if so, whether it is odd or even.

Handle cases where there are no numbers or where the last column is empty.

Sample Data

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In this file:

The first line has the number 123 (which is odd).

The second line has 234 (which is even).

The third line is missing a number.

Creating the Bash Script

Let’s walk through the steps to write this Bash script.

Step 1: Initialize the Script

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Step 2: Check Each Line for Last Column

We’ll use a loop to read each line of the file and extract the last column. Here's the first part of your script to check for numbers in the last column.

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Step 3: Input and Output Explanation

IFS=' ': This sets the Internal Field Separator to a space, allowing you to read columns easily.

array[-1]: This retrieves the last element from an array formed by splitting the line.

Checks:

If the last column is empty, it outputs "not found."

If it’s not a number, it informs you via error output.

It checks if the number is odd or even using the modulo operator.

Running Your Script

Make sure your script has execute permissions, then run it:

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Expected Output

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Conclusion

By following this guide, you created a Bash script capable of reading a file and analyzing the last column for whether numbers are odd, even, or not present. This script can be modified and used for various other data processing tasks.

Feel free to adapt the code for your specific needs, and happy scripting!