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std::basic_...buf::is_open(3)  C++ Standard Libary std::basic_...buf::is_open(3)

NAME
     std::basic_filebuf::is_open - std::basic_filebuf::is_open

Synopsis
	bool is_open() const;

	Returns  true  if the most recent call to open() succeeded and there has
     been no call
	to close() since then.

Parameters
	(none)

Return value
	true if the associated file is open, false otherwise.

Notes
	This function is typically called by std::basic_fstream::is_open().

Example
     // Run this code

      #include <fstream>
      #include <iostream>

      int main()
      {
	  std::ifstream fs("test.txt");
	  std::filebuf fb;
	  fb.open("test.txt", std::ios_base::in);
	  std::cout << std::boolalpha
		    << "direct call: " << fb.is_open() << '\n'
		    << "through streambuf: " << fs.rdbuf()->is_open() << '\n'
		    << "through fstream: " << fs.is_open() << '\n';
      }

Output:
      direct call: true
      through streambuf: true
      through fstream: true

See also
	open  opens a file and configures it as  the  associated  character  se-
     quence
	      (public member function)
	close flushes the put area buffer and closes the associated file
	      (public member function)

http://cppreference.com 	   2024.06.10	   std::basic_...buf::is_open(3)
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