How to Compare Two Files in Linux and Summarize Answers for a Script

Discover how to efficiently compare two files containing simple `YES` or `NO` answers in Linux, and store results in variables for further use.
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Comparing Two Files in Linux: A Quick Guide to Summarizing Answers

When working with script files in Linux, you might encounter situations where you need to compare the contents of two files. For instance, you may have two files that contain responses such as "YES" or "NO," and you want to determine how many answers were correct and how many were incorrect. This process of comparison is straightforward, but it can take a bit of finesse to ensure you are storing the results correctly for later use. In this guide, we will explore how to effectively compare two files, summarize the results, and store them in variables.

The Problem: Comparing Two Files

You have two files that each contain ten lines of simple answers. You need to:

Count the number of correct answers (YES)

Count the number of incorrect answers (NO)

Store these counts in variables for later use without displaying them on the console

In other words, your goal is not just to see the difference visually, but to programmatically assess and save the results.

The Solution: Using Bash Commands

To achieve this, you can leverage the power of the diff, nl, and grep commands in your script. Below is a step-by-step breakdown of how to accomplish this.

Step 1: Using diff, nl, and grep

Here’s how you can use the diff command combined with nl (to number lines) and grep to track differences. Here's the important command you will use:

[[See Video to Reveal this Text or Code Snippet]]

diff <(nl $1) <(nl $2): This part compares the two files line by line.

grep -E '<': This filters the output of diff to show only lines where the first file has a discrepancy.

wc -l: This counts the number of lines returned by grep, which corresponds to incorrect answers.

Step 2: Storing Results in Variables

To store the count of bad answers in a variable, you simply set the command output to a variable as shown above.

Next, to count good answers, you would subtract the count of bad answers from the total number of responses (10 in this case):

[[See Video to Reveal this Text or Code Snippet]]

Complete Example

Putting it all together, your script would look something like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By using a few simple commands, you can effectively compare two files and summarize the results. This method not only helps you identify correct and incorrect answers but also allows you to store these results in variables for further processing in your script.

Remember, mastering command-line tools can save you time and automate tedious tasks. Happy scripting!