How Can I Correctly Write Strings to Files in C ?

Writing Strings to Files in C

When handling user input in the form of strings, it's common to want to write them to a file for storage. However, attempting to do so using the write() method of an ofstream can lead to unexpected results.

std::string and File Writing

It's important to understand that std::string is a complex data structure that stores both the string's value and its length internally. When using write() with std::string, it actually writes this internal representation to the file. This binary data is unlikely to be displayed correctly as text when the file is opened.

Using an ofstream for Text Files

For writing plaintext to files, the recommended approach is to use an ofstream object, which acts like a std::cout for writing to files. The following code sample illustrates this approach:

#include <fstream>
#include <iostream>

int main() {
    std::string studentName;
    std::cout << "Enter your name: ";
    std::cin >> studentName;

    std::ofstream outFile("output.txt");
    outFile << studentName;
    outFile.close();

    return 0;
}

Writing Binary Data to Files

If you need to write the actual binary representation of the string, rather than its plaintext value, you can use string::c_str() to retrieve a pointer to the raw data and its length for write(). The following snippet demonstrates this:

write.write(studentPassword.c_str(), studentPassword.size());

By using these techniques, you can effectively write both plaintext strings and binary data to files, depending on your specific requirements.

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