Скачать или смотреть How to Create a Looping Input Program in C to Write to a File Until "end" is Typed

Learn how to write a C program that repeatedly asks for user input and saves it to a file until the user types "end". This guide provides clear steps and explanations for beginners.
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Creating a Looping Input Program in C

As a beginner in programming, you might encounter challenges when trying to create programs that require continuous user interaction. One common task is writing a program in C that allows users to type strings of text and saves that input to a file. The program should continue to ask for input until the user types a specific keyword, such as "end". If you're struggling with this, fret not! This post will walk you through the solution step by step.

The Problem

You want to create a C program where:

The user can enter strings of text repeatedly.

Each string entered by the user should be saved to a file named output.txt.

The program should stop asking for input when the user types "end".

You may have already attempted to write your code, but it might be running into an issue where it gets stuck in a loop after the first input. This commonly happens because of how input is handled in C.

Solution Explanation

Understanding the Input Issue

In your current code, you used the following line to read input:

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

This command works well for capturing user input until a newline character is detected, but it retains that newline character in the input buffer after the first input. As a result, the program repeatedly encounters that newline on subsequent iterations, which disrupts further input capture.

Updating Your Input Method

To fix this issue, you can modify the scanf line to ignore leading whitespace (including the newline character left from the previous input) by adding a space before the format specifier. Update your code as follows:

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

This change means that scanf will skip any whitespace characters, so it won’t be affected by the newline character. As a result, the program can correctly read subsequent inputs.

Complete Code Example

Here’s the full corrected code with the mentioned changes:

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

Key Changes Made

Improved Input Handling: By changing scanf("%[^\n]", text); to scanf(" %[^\n]", text);, the program now correctly captures user inputs without getting stuck.

File Management: Ensure the file is opened in append mode, allowing additional texts to be added without overwriting existing contents.

Loop Control: The program loops until "end" is typed in, providing a seamless user experience.

Conclusion

Developing a C program that handles continuous user input and writes it to a file can be daunting at first, especially for new programmers. However, understanding how input handling works and modifying your scanf function can resolve common issues. Follow this guide, use the provided code, and you'll have a working program that meets your requirements. Happy coding!