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std::ios_base::openmode

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 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

#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

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>`)

std::ios_base::openmode

Example

See also