NAME¶

std::basic_ifstream::is_open - std::basic_ifstream::is_open

Synopsis¶

bool is_open() const;

Checks if the file stream has an associated file.

Effectively calls rdbuf()->is_open().

Parameters¶

(none)

Return value¶

true if the file stream has an associated file, false otherwise.

Example¶

// Run this code

#include <fstream>
#include <iostream>
#include <string>

// this file is called main.cpp

bool file_exists(const std::string& str)
{
std::ifstream fs(str);
return fs.is_open();
}

int main()
{
std::boolalpha(std::cout);
std::cout << file_exists("main.cpp") << '\n'
<< file_exists("strange_file") << '\n';
}

Possible output:¶

true
false

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 365 C++98 is_open was not declared with const qualifier declared with const
qualifier

See also¶

open opens a file and associates it with the stream
(public member function)
close closes the associated file
(public member function)