Should I Manually Close an `ifstream` in C ?

Do I Need to Manually Close an ifstream?

In C , Resources Acquisition Is Initialization (RAII) ensures that objects are automatically cleaned up and released when they go out of scope. This mechanism is employed in various classes, including std::ifstream.

When an std::ifstream object is created, it opens the specified file for input. By default, the file remains open until the object is destroyed. However, a common question arises: should I explicitly call file.close() manually or can I rely on RAII to handle it?

The answer is NO.

RAII and ifstream

The purpose of RAII is precisely to alleviate the need for manual resource cleanup. In the case of ifstream, the destructor is responsible for closing the associated file, making explicit calls to file.close() unnecessary.

In the example code provided, the file object is declared within the scope of the readContentsOfFile() function. When the function returns, the object goes out of scope, and the destructor is called automatically. This ensures that the file is closed before the function exits.

Nested Scope for Early Closure

While RAII guarantees file closure upon object destruction, it may be desirable to close the file earlier within a function. This can be achieved using a nested scope:

{
    std::ifstream file(fileName.c_str());

    if (file.good()) {
        std::stringstream buffer;
        buffer << file.rdbuf();
    }

    file.close();
}

Within the nested scope, the file object is created and opened. If the file is valid, it is processed immediately, and the file is closed before the inner scope ends.

Conclusion

std::ifstream already takes care of file closure through RAII. Manual calls to file.close() are unnecessary and should be avoided as they violate the principles of RAII in C .

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