Does `std::ifstream` Automatically Close Files Upon Destruction?

Do ifstream Destructors Close Files Automatically?

When utilizing std::ifstream streams, the question arises: is it necessary to explicitly invoke the close() method?

As illustrated in the provided code snippet:

std::string readContentsOfFile(std::string fileName) {

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

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

      return buffer.str();
  }
  throw std::runtime_exception("file not found");
}

Is the explicit call to file.close() essential or is RAII capable of handling file closure?

Answer: No

RAII, or Resource Acquisition Is Initialization, is a C paradigm that ensures the proper cleanup and deallocation of resources through destructors. In the case of ifstream, the file handle is a resource acquired during its construction. When the ifstream object goes out of scope, its destructor is called, which in turn closes the file handle. In essence, RAII automates this task, making manual closure unnecessary.

While it may not cause harm to invoke file.close() explicitly, it is considered good practice to allow RAII to fulfill its intended purpose. Manual closure in C code can be seen as a carryover from C-style programming.

If the need arises to prematurely close a file within the scope of a function, nesting scopes is a viable solution:

{
  std::ifstream file(fileName.c_str());
  if (/*some condition*/) {
    file.close();
  }
}

The ifstream's destructor, activated by leaving the inner scope, will close the file regardless of the condition.

In conclusion, std::ifstream objects employ RAII to automatically close files when they go out of scope, eliminating the need for manual cleanup. Embracing this principle promotes clean and efficient C coding.

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