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std::basic_ifstream<CharT,Traits>::is_open

From cppreference.com
< cpp‎ | io‎ | basic ifstream
 
 
 
 
bool is_open() const;

Checks if the file stream has an associated file.

Effectively calls rdbuf()->is_open().

Contents

[edit] Parameters

(none)

[edit] Return value

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

[edit] Example

#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

[edit] 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

[edit] See also

opens a file and associates it with the stream
(public member function) [edit]
closes the associated file
(public member function) [edit]