std::basic_fstream<CharT,Traits>::is_open
From cppreference.com
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>
int main()
{
std::string filename = "some_file";
std::fstream fs(filename, std::ios::in);
std::cout << std::boolalpha;
std::cout << "fs.is_open() = " << fs.is_open() << '\n';
if (!fs.is_open())
{
fs.clear();
fs.open(filename, std::ios::out);
std::cout << "fs.is_open() = " << fs.is_open() << '\n';
}
}
Possible output:
fs.is_open() = false
fs.is_open() = true
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
| opens a file and associates it with the stream (public member function) | |
| closes the associated file (public member function) |