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std::ofstream::is_open
C++98C++11
bool is_open();
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 // std::cout
#include // 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;
}
Edit & Run

Possible output:
Output operation successfully performed

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

Exception safety