How to Use a case Statement with Variables and User Input in Bash Scripts

Discover how to implement a `case` statement in your Bash script to handle user input for logging quantities efficiently! Our guide provides step-by-step instructions and expert tips.
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How to Use a case Statement with Variables and User Input in Bash Scripts

When working with Bash scripting, you may come across situations where you want to execute different parts of your code based on user input. This is where the case statement shines. In this guide, we'll discuss how to effectively implement a case statement in a Bash script that logs quantities of items—both positive and negative—based on user interaction. Let’s dive in!

The Problem

You’re building a Bash script that logs simple information into a CSV file. The script prompts the user to choose an option to either add or remove items. Specifically:

Pressing * represents a decrease (minus).

Pressing - represents an increase (plus).

After the user chooses one of these buttons, they will enter a quantity, which should then be logged effectively. If the user inputs something invalid, the script should prompt them again for a valid option.

The Solution

Let's break down the solution into manageable sections.

Step 1: Initialize the Script

Start your script with the shebang line to specify which interpreter to use:

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

Step 2: Set Up the Infinite Loop

You will need a loop to keep asking the user for input until a valid option is provided:

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

Step 3: Prompt the User

Inside the loop, you can prompt the user for input:

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

Step 4: Read User Input

Use the read command to capture user input. It’s a good idea to redirect from /dev/tty to ensure that the input is read from the terminal correctly:

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

Step 5: Implement the Case Statement

This is where the magic happens! Use a case statement to handle the user's input:

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

Handling Different Inputs

Each potential input can be handled as follows:

For Minus Option (*):

Check if the next input is a number.

Log it using the echo command to a CSV file.

For Plus Option (-):

Similar to the minus option, check for valid numeric input and log it.

Handle Invalid Inputs: If the user enters anything other than the expected characters, provide feedback and prompt again.

Here’s how this might look in code:

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

Complete Script Example

Here is how the entire script would look:

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

Conclusion

Implementing a case statement in your Bash scripts can significantly improve user interaction. By grouping similar conditions together, your code becomes cleaner and easier to manage. We hope this guide has helped you understand how to use a case statement with variables and user input effectively!

For any further questions or clarifications, feel free to leave a comment below!