std::basic_fstream<CharT,Traits>::open
void open( const char* filename, std::ios_base::openmode mode = std::ios_base::in | std::ios_base::out ); |
(1) | |
void open( const std::filesystem::path::value_type* filename, std::ios_base::openmode mode = std::ios_base::in | std::ios_base::out ); |
(2) | (since C++17) |
void open( const std::string& filename, std::ios_base::openmode mode = std::ios_base::in | std::ios_base::out ); |
(3) | (since C++11) |
void open( const std::filesystem::path& filename, std::ios_base::openmode mode = std::ios_base::in | std::ios_base::out ); |
(4) | (since C++17) |
Opens and associates the file with name filename with the file stream.
Calls clear() on success. Calls setstate(failbit) on failure.
std::filesystem::path::value_type
is not char. (since C++17)Contents |
[edit] Parameters
filename | - | the name of the file to be opened | ||||||||||||||||
mode | - | specifies stream open mode. It is a BitmaskType, the following constants are defined:
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[edit] Return value
(none)
[edit] Example
#include <string> #include <fstream> #include <iostream> int main() { std::string filename = "example.123"; std::fstream fs; fs.open(filename); if (!fs.is_open()) { fs.clear(); fs.open(filename, std::ios::out); // create file fs.close(); fs.open(filename); } std::cout << std::boolalpha; std::cout << "fs.is_open() = " << fs.is_open() << '\n'; std::cout << "fs.good() = " << fs.good() << '\n'; }
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 22 | C++98 | it was unclear how error state changes upon a successful open | the error state is unchanged |
LWG 409 | C++98 | the error state was unchanged upon a successful open | it is cleared[1] |
- ↑ The resolution of LWG issue #22 is overriden.
[edit] See also
checks if the stream has an associated file (public member function) | |
closes the associated file (public member function) | |
opens a file and configures it as the associated character sequence (public member function of std::basic_filebuf<CharT,Traits> )
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