C++

Reference

<fstream>

ofstream

public member function
<fstream>

std::ofstream::is_open

bool is_open();
bool is_open() const;
Check if file is open
Returns whether the stream is currently associated to a file.

Streams can be associated to files by a successful call to member open or directly on construction, and disassociated by calling close or on destruction.

The file association of a stream is kept by its internal stream buffer:
Internally, the function calls rdbuf()->is_open()

Parameters

none

Return Value

true if a file is open and associated with this stream object.
false otherwise.

Example

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// ofstream::is_open #include <iostream> // std::cout #include <fstream> // std::ofstream int main () { std::ofstream ofs; ofs.open ("test.txt"); if (ofs.is_open()) { ofs << "lorem ipsum"; std::cout << "Output operation successfully performed\n"; ofs.close(); } else { std::cout << "Error opening file"; } return 0; }

Possible output:
Output operation successfully performed


Data races

Accesses the ofstream object.
Concurrent access to the same stream may introduce data races.

Exception safety

Strong guarantee: if an exception is thrown, there are no changes in the stream.

See also

ofstream::open
Open file (public member function)
ofstream::close
Close file (public member function)
filebuf::is_open
Check if a file is open (public member function)