Creating a Safe and Interactive Menu in C Using fgets

Описание: Learn how to build a robust menu system in C using `fgets` for input instead of `scanf`, ensuring better safety and user interaction.
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This video is based on the question https://stackoverflow.com/q/65498103/ asked by the user 'Hugo' ( https://stackoverflow.com/u/14909422/ ) and on the answer https://stackoverflow.com/a/65509253/ provided by the user 'Hugo' ( https://stackoverflow.com/u/14909422/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Creating a Safe and Interactive Menu in C Using fgets

When developing applications in C, one of the essential tasks is to create a menu system that allows users to interact with the program seamlessly. Traditionally, scanf has been used for input, but it can be less safe due to its inability to handle incorrect input gracefully. Instead, using fgets can help mitigate these issues, but it comes with its own challenges. In this post, we will go through a common problem encountered when using fgets and how to effectively implement it in a menu-driven program.

The Problem with scanf

Using scanf can lead to several problems:

Buffer Overflow: If the user inputs more characters than expected, it can lead to memory issues.

Input Errors: If the user enters a non-numeric value where a number is expected, scanf may not handle this elegantly, which can cause problems in your program.

To solve these issues, we leverage fgets to read input safely, but this requires a few additional steps, notably converting the string input into an integer for menu selection.

Initial Code Structure

Here’s a look at the original attempt at creating a menu using a loop and fgets:

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In this code, the program does not wait for input due to a misplaced semicolon which causes an issue in the loop’s condition and flow.

Effective Solution Using fgets

To solve these issues, we can utilize fgets correctly alongside a do-while loop, thus ensuring that the program continues to prompt the user until they exit. Here's the revised version of the code:

Correct Code Implementation

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

Key Modifications

Using do-while Instead of while:

This guarantees that the menu will always be displayed at least once.

Converting String to Integer:

The use of atoi to convert the character array (cVal) to an integer (menyVal) which controls the flow through the switch statement.

Removing the Erroneous Semicolon:

The semicolon on the while statement was removed to ensure proper flow of the input loop.

Conclusion

By adopting fgets for reading user input in C, you create a safer environment that minimizes the risk of input errors and buffer overflows. This combined with the structured handling of input loop logic ensures a better user experience. With these improvements, your menu-driven applications can now function more reliably and robustly.

Now you can effectively manage user input in a C program with a menu that feels intuitive and safe! Happy coding!