31 Input/output library [input.output]

31.10 File-based streams [file.streams]

31.10.4 Class template basic_ofstream [ofstream]

31.10.4.1 General [ofstream.general]

namespace std { template<class charT, class traits = char_traits<charT>> class basic_ofstream : public basic_ostream<charT, traits> { public: using char_type = charT; using int_type = typename traits::int_type; using pos_type = typename traits::pos_type; using off_type = typename traits::off_type; using traits_type = traits; // [ofstream.cons], constructors basic_ofstream(); explicit basic_ofstream(const char* s, ios_base::openmode mode = ios_base::out); explicit basic_ofstream(const filesystem::path::value_type* s, // wide systems only; see [fstream.syn] ios_base::openmode mode = ios_base::out); explicit basic_ofstream(const string& s, ios_base::openmode mode = ios_base::out); template<class T> explicit basic_ofstream(const T& s, ios_base::openmode mode = ios_base::out); basic_ofstream(const basic_ofstream&) = delete; basic_ofstream(basic_ofstream&& rhs); basic_ofstream& operator=(const basic_ofstream&) = delete; basic_ofstream& operator=(basic_ofstream&& rhs); // [ofstream.swap], swap void swap(basic_ofstream& rhs); // [ofstream.members], members basic_filebuf<charT, traits>* rdbuf() const; bool is_open() const; void open(const char* s, ios_base::openmode mode = ios_base::out); void open(const filesystem::path::value_type* s, ios_base::openmode mode = ios_base::out); // wide systems only; see [fstream.syn] void open(const string& s, ios_base::openmode mode = ios_base::out); void open(const filesystem::path& s, ios_base::openmode mode = ios_base::out); void close(); private: basic_filebuf<charT, traits> sb; // exposition only }; }

The class basic_ofstream<charT, traits> supports writing to named files.

It uses a basic_filebuf<charT, traits> object to control the associated sequence.

For the sake of exposition, the maintained data is presented here as:

(1.1)
sb, the filebuf object.

31.10.4.2 Constructors [ofstream.cons]

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basic_ofstream();

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream.cons]) and sb with basic_filebuf<charT, traits>() ([filebuf.cons]).

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explicit basic_ofstream(const char* s,
                        ios_base::openmode mode = ios_base::out);
explicit basic_ofstream(const filesystem::path::value_type* s,
                        ios_base::openmode mode = ios_base::out); // wide systems only; see [fstream.syn]

Effects: Initializes the base class with basic_ostream<charT, traits>(addressof(sb)) ([ostream.cons]) and sb with basic_filebuf<charT, traits>() ([filebuf.cons]), then calls rdbuf()->open(s, mode | ios_base::out).

If that function returns a null pointer, calls setstate(failbit).

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explicit basic_ofstream(const string& s,
                        ios_base::openmode mode = ios_base::out);

Effects: Equivalent to: basic_ofstream(s.c_str(), mode).

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template<class T>
  explicit basic_ofstream(const T& s, ios_base::openmode mode = ios_base::out);

Constraints: is_same_v<T, filesystem::path> is true.

Effects: Equivalent to: basic_ofstream(s.c_str(), mode).

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basic_ofstream(basic_ofstream&& rhs);

Effects: Move constructs the base class, and the contained basic_filebuf.

Then calls basic_ostream<charT, traits>::set_rdbuf(addressof(sb)) to install the contained basic_filebuf.

31.10.4.3 Swap [ofstream.swap]

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void swap(basic_ofstream& rhs);

Effects: Exchanges the state of *this and rhs by calling basic_ostream<charT, traits>::swap(rhs) and sb.swap(rhs.sb).

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template<class charT, class traits>
  void swap(basic_ofstream<charT, traits>& x, basic_ofstream<charT, traits>& y);

Effects: Equivalent to: x.swap(y).

31.10.4.4 Member functions [ofstream.members]

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basic_filebuf<charT, traits>* rdbuf() const;

Returns: const_cast<basic_filebuf<charT, traits>*>(addressof(sb)).

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bool is_open() const;

Returns: rdbuf()->is_open().

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void open(const char* s, ios_base::openmode mode = ios_base::out);
void open(const filesystem::path::value_type* s,
          ios_base::openmode mode = ios_base::out);             // wide systems only; see [fstream.syn]

Effects: Calls rdbuf()->open(s, mode | ios_base::out).

If that function does not return a null pointer calls clear(), otherwise calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).

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void close();

Effects: Calls rdbuf()->close() and, if that function fails (returns a null pointer), calls setstate(failbit) (which may throw ios_base::failure) ([iostate.flags]).

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void open(const string& s, ios_base::openmode mode = ios_base::out);
void open(const filesystem::path& s, ios_base::openmode mode = ios_base::out);

Effects: Calls open(s.c_str(), mode).