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std::basic_...eam::is_open(3)  C++ Standard Libary std::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		    Cor-
     rect behavior
	LWG  365  C++98       is_open  was not declared with const qualifier de-
     clared with const
									 quali-
     fier

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)
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