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std::basic_...eam::is_open(3) C++ Standard Libarystd::basic_...eam::is_open(3) NAME std::basic_fstream::is_open - std::basic_fstream::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> 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 retroac- tively 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 de- clared with const qual- ifier See also open opens a file and associates it with the stream (public member function) close closes the associated file (public member function) http://cppreference.com 2024.06.10 std::basic_...eam::is_open(3)
NAME | Synopsis | Parameters | Return value | Example | Possible output: | See also
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