[ofstream] # 31 Input/output library [[input.output]](./#input.output) ## 31.10 File-based streams [[file.streams]](file.streams#ofstream) ### 31.10.5 Class template basic_ofstream [ofstream] #### [31.10.5.1](#general) General [[ofstream.general]](ofstream.general) [🔗](#lib:basic_ofstream) namespace std {template>class basic_ofstream : public basic_ostream {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; using native_handle_type = typename basic_filebuf::native_handle_type; // [[ofstream.cons]](#cons "31.10.5.2 Constructors"), 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]](fstream.syn "31.10.1 Header synopsis") ios_base::openmode mode = ios_base::out); explicit basic_ofstream(const string& s, ios_base::openmode mode = ios_base::out); templateexplicit 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 "31.10.5.3 Swap"), swapvoid swap(basic_ofstream& rhs); // [[ofstream.members]](#members "31.10.5.4 Member functions"), members basic_filebuf* rdbuf() const; native_handle_type native_handle() const noexcept; 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]](fstream.syn "31.10.1 Header synopsis")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 *sb*; // *exposition only*};} [1](#general-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12080) The classbasic_ofstream supports writing to named files[.](#general-1.sentence-1) It uses abasic_filebuf<​charT, traits> object to control the associated sequence[.](#general-1.sentence-2) For the sake of exposition, the maintained data is presented here as: - [(1.1)](#general-1.1) *sb*, the filebuf object[.](#general-1.sentence-3) #### [31.10.5.2](#cons) Constructors [[ofstream.cons]](ofstream.cons) [🔗](#lib:basic_ofstream,constructor) `basic_ofstream(); ` [1](#cons-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12102) *Effects*: Initializes the base class withbasic_ostream(addressof(*sb*)) ([[ostream.cons]](ostream.cons "31.7.6.2.2 Constructors")) and *sb* withbasic_filebuf() ([[filebuf.cons]](filebuf.cons "31.10.3.2 Constructors"))[.](#cons-1.sentence-1) [🔗](#lib:basic_ofstream,constructor_) `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]](fstream.syn "31.10.1 Header synopsis") ` [2](#cons-2) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12119) *Effects*: Initializes the base class withbasic_ostream(addressof(*sb*)) ([[ostream.cons]](ostream.cons "31.7.6.2.2 Constructors")) and *sb* withbasic_filebuf() ([[filebuf.cons]](filebuf.cons "31.10.3.2 Constructors")), then callsrdbuf()->open(s, mode | ios_base​::​out)[.](#cons-2.sentence-1) If that function returns a null pointer, callssetstate(​failbit)[.](#cons-2.sentence-2) [🔗](#lib:basic_ofstream,constructor__) `explicit basic_ofstream(const string& s, ios_base::openmode mode = ios_base::out); ` [3](#cons-3) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12138) *Effects*: Equivalent to basic_ofstream(s.c_str(), mode)[.](#cons-3.sentence-1) [🔗](#lib:basic_ofstream,constructor___) `template explicit basic_ofstream(const T& s, ios_base::openmode mode = ios_base::out); ` [4](#cons-4) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12150) *Constraints*: is_same_v is true[.](#cons-4.sentence-1) [5](#cons-5) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12154) *Effects*: Equivalent to basic_ofstream(s.c_str(), mode)[.](#cons-5.sentence-1) [🔗](#lib:basic_ofstream,constructor____) `basic_ofstream(basic_ofstream&& rhs); ` [6](#cons-6) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12165) *Effects*: Move constructs the base class, and the contained basic_filebuf[.](#cons-6.sentence-1) Then calls basic_ostream​::​set_rdbuf(​addressof(*sb*)) to install the contained basic_filebuf[.](#cons-6.sentence-2) #### [31.10.5.3](#swap) Swap [[ofstream.swap]](ofstream.swap) [🔗](#lib:swap,basic_ofstream) `void swap(basic_ofstream& rhs); ` [1](#swap-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12180) *Effects*: Exchanges the state of *this and rhs by callingbasic_ostream​::​swap(rhs) and*sb*.swap(rhs.*sb*)[.](#swap-1.sentence-1) [🔗](#lib:swap,basic_ofstream_) `template void swap(basic_ofstream& x, basic_ofstream& y); ` [2](#swap-2) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12195) *Effects*: Equivalent to x.swap(y)[.](#swap-2.sentence-1) #### [31.10.5.4](#members) Member functions [[ofstream.members]](ofstream.members) [🔗](#lib:rdbuf,basic_ofstream) `basic_filebuf* rdbuf() const; ` [1](#members-1) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12208) *Returns*: const_cast*>(addressof(*sb*))[.](#members-1.sentence-1) [🔗](#lib:native_handle,basic_ofstream) `native_handle_type native_handle() const noexcept; ` [2](#members-2) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12219) *Effects*: Equivalent to: return rdbuf()->native_handle(); [🔗](#lib:is_open,basic_ofstream) `bool is_open() const; ` [3](#members-3) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12230) *Returns*: rdbuf()->is_open()[.](#members-3.sentence-1) [🔗](#lib:open,basic_ofstream) `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]](fstream.syn "31.10.1 Header synopsis") ` [4](#members-4) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12243) *Effects*: Callsrdbuf()->open(s, mode | ios_base​::​out)[.](#members-4.sentence-1) If that function does not return a null pointer calls clear(), otherwise callssetstate(​failbit) (which may throwios_base​::​failure) ([[iostate.flags]](iostate.flags "31.5.4.4 Flags functions"))[.](#members-4.sentence-2) [🔗](#lib:close,basic_ofstream) `void close(); ` [5](#members-5) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12261) *Effects*: Callsrdbuf()->close() and, if that function fails (returns a null pointer), callssetstate(​failbit) (which may throwios_base​::​failure) ([[iostate.flags]](iostate.flags "31.5.4.4 Flags functions"))[.](#members-5.sentence-1) [🔗](#lib:open,basic_ofstream_) `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); ` [6](#members-6) [#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L12278) *Effects*: Calls open(s.c_str(), mode)[.](#members-6.sentence-1)