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std::ios_base::openmode(3)    C++ Standard Libary   std::ios_base::openmode(3)

NAME
       std::ios_base::openmode - std::ios_base::openmode

Synopsis
	  typedef /* implementation defined */ openmode;
	  static constexpr openmode app	      =	/* implementation defined */;

	  static constexpr openmode binary    =	/* implementation defined */;
	  static constexpr openmode in	      =	/* implementation defined */;
	  static constexpr openmode out	      =	/* implementation defined */;
	  static constexpr openmode trunc     =	/* implementation defined */;

	  static constexpr openmode ate	      =	/* implementation defined */;
	  static  constexpr openmode noreplace = /* implementation defined */;
       (since C++23)

	  Specifies available file open	flags. It is a BitmaskType,  the  fol-
       lowing constants
	  are defined:

	  Constant	    Explanation
	  app		    seek to the	end of stream before each write
	  binary	    open in binary mode
	  in		    open for reading
	  out		    open for writing
	  trunc		    discard the	contents of the	stream when opening
	  ate		    seek to the	end of stream immediately after	open
	  noreplace (C++23) open in exclusive mode

Example
       // Run this code

	#include <fstream>
	#include <iostream>
	#include <string>

	int main()
	{
	    const char*	fname =	"unique_name.txt";

	    // write to	a temporary stream object
	    std::fstream(fname,	std::ios::out |	std::ios::trunc) << "Hi";

	    std::string	s;
	    std::fstream(fname,	std::ios::in) >> s;
	    std::cout << s << '\n';
	}

Output:
	Hi

See also
	  open		opens a	file and configures it as the associated char-
       acter sequence
			(public	   member    function	 of   std::basic_file-
       buf<CharT,Traits>)
			constructs a basic_stringbuf object
	  constructor	(public	member function	of
			std::basic_stringbuf<CharT,Traits,Allocator>)

http://cppreference.com		  2024.06.10	    std::ios_base::openmode(3)

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