std::ios_base::openmode

 

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typedef/* implementation defined */ openmode;
staticconstexpr openmode app       =/* implementation defined */; staticconstexpr openmode binary    =/* implementation defined */; staticconstexpr openmode in        =/* implementation defined */; staticconstexpr openmode out       =/* implementation defined */; staticconstexpr openmode trunc     =/* implementation defined */; staticconstexpr openmode ate       =/* implementation defined */;
staticconstexpr openmode noreplace =/* implementation defined */;		(since C++23)

Specifies available file open flags. It is a BitmaskType, the following 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(){constchar* fname ="unique_name.txt";   // write to a temporary stream objectstd::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 character sequence (public member function of std::basic_filebuf<CharT,Traits>)
(constructor)	constructs a basic_stringbuf object (public member function of std::basic_stringbuf<CharT,Traits,Allocator>)