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

NAME
       std::basic_ifstream::is_open - std::basic_ifstream::is_open

Synopsis
	  bool is_open();	 (until	C++11)
	  bool is_open() const;	 (since	C++11)

	  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 <string>
	#include <fstream>
	#include <iostream>
	//this file is called main.cpp

	bool file_exists(const std::string& str)
	{
	   std::ifstream fs(str);
	   return fs.is_open();
	}

	int main()
	{
	  std::boolalpha(std::cout);
	  std::cout << file_exists("main.cpp")	<< '\n'
		    << file_exists("strange_file") << '\n';
	}

Possible output:
	true
	false

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		  2022.07.31	  std::basic_...am::is_open(3)

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<https://man.freebsd.org/cgi/man.cgi?query=std::wifstream::is_open&sektion=3&manpath=FreeBSD+Ports+15.0>

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