std::ifstream initialization with filename

Question

I am using the following piece of code to check whether file is existing or not using

std::ifstream

.

#include <iostream>

#include <fstream>



int main()

{

    if (std::ifstream("file.txt"))

    {

        std::cout << "File present\n";

    }



    return 0;

}

Since I am not using any object for

std::ifstream

, how do I close the file? Or is it not required to call close?

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Answer 1

Actually you are using unnamed temporary object of std::ifstream. It is not required to call std::ifstream::close(), as the object is being destroyed after usage, and it's destructor closes the file correctly.

To be more precise:

// Temporary object is not yet created here
if (std::ifstream("file.txt"))
{
    // Temporary object is already destroyed here
    std::cout << "File present\n";
}
// Or here

From documentation:

(destructor)[virtual] (implicitly declared)

destructs the basic_ifstream and the associated buffer, closes the file

std::ifstream initialization with filename

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