# Standard library header <ostream>

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< cpp‎ | header

This header is part of the Input/output library.

### Classes
basic_ostream | wraps a given abstract device (std::basic_streambuf) and provides high-level output interface (class template)
std::ostream | std::basic_ostream<char> (typedef)
std::wostream | std::basic_ostream<wchar_t> (typedef)
### Functions
operator<<(std::basic_ostream) | inserts character data or insert into rvalue stream (function template)
print(std::ostream) (C++23) | outputs formatted representation of the arguments (function template)
println(std::ostream) (C++23) | outputs formatted representation of the arguments with appended '\n' (function template)
vprint_unicode(std::ostream) (C++23) | performs Unicode aware output using type-erased argument representation (function)
vprint_nonunicode(std::ostream) (C++23) | outputs character data using type-erased argument representation (function)
##### Manipulators
endl | outputs '\n' and flushes the output stream (function template)
ends | outputs '\0' (function template)
flush | flushes the output stream (function template)
emit_on_flush noemit_on_flush (C++20) | controls whether a stream's `basic_syncbuf` emits on flush (function template)
flush_emit (C++20) | flushes a stream and emits the content if it is using a `basic_syncbuf` (function template)

### Synopsis

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
        class basic_ostream;

      using ostream  = basic_ostream<char>;
      using wostream = basic_ostream<wchar_t>;

      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& endl(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& ends(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& flush(basic_ostream<CharT, Traits>& os);

      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& emit_on_flush(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& noemit_on_flush(basic_ostream<CharT, Traits>& os);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& flush_emit(basic_ostream<CharT, Traits>& os);

      template<class Ostream, class T>
        Ostream&& operator<<(Ostream&& os, const T& x);

      // print functions
      template<class... Args>
        void print(ostream& os, format_string<Args...> fmt, Args&&... args);
      template<class... Args>
        void println(ostream& os, format_string<Args...> fmt, Args&&... args);

      void vprint_unicode(ostream& os, string_view fmt, format_args args);
      void vprint_nonunicode(ostream& os, string_view fmt, format_args args);
    }

#### Class template std::basic_ostream

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
      class basic_ostream : virtual public basic_ios<CharT, Traits> {
      public:
        // types (inherited from basic_ios)
        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;

        // constructor/destructor
        explicit basic_ostream(basic_streambuf<char_type, Traits>* sb);
        virtual ~basic_ostream();

        // prefix/suffix
        class sentry;

        // formatted output
        basic_ostream& operator<<(basic_ostream& (*pf)(basic_ostream&));
        basic_ostream& operator<<(basic_ios<CharT, Traits>& (*pf)(basic_ios<CharT, Traits>&));
        basic_ostream& operator<<(ios_base& (*pf)(ios_base&));

        basic_ostream& operator<<(bool n);
        basic_ostream& operator<<(short n);
        basic_ostream& operator<<(unsigned short n);
        basic_ostream& operator<<(int n);
        basic_ostream& operator<<(unsigned int n);
        basic_ostream& operator<<(long n);
        basic_ostream& operator<<(unsigned long n);
        basic_ostream& operator<<(long long n);
        basic_ostream& operator<<(unsigned long long n);
        basic_ostream& operator<<(float f);
        basic_ostream& operator<<(double f);
        basic_ostream& operator<<(long double f);
        basic_ostream& operator<<(/*extended-floating-point-type*/ f);

        basic_ostream& operator<<(const void* p);
        basic_ostream& operator<<(const volatile void* p);
        basic_ostream& operator<<(nullptr_t);
        basic_ostream& operator<<(basic_streambuf<char_type, Traits>* sb);

        // unformatted output
        basic_ostream& put(char_type c);
        basic_ostream& write(const char_type* s, streamsize n);

        basic_ostream& flush();

        // seeks
        pos_type tellp();
        basic_ostream& seekp(pos_type);
        basic_ostream& seekp(off_type, ios_base::seekdir);

      protected:
        // copy/move constructor
        basic_ostream(const basic_ostream&) = delete;
        basic_ostream(basic_ostream&& rhs);

        // assignment and swap
        basic_ostream& operator=(const basic_ostream&) = delete;
        basic_ostream& operator=(basic_ostream&& rhs);
        void swap(basic_ostream& rhs);
      };

      // character inserters
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& operator<<(basic_ostream<CharT, Traits>&, CharT);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& operator<<(basic_ostream<CharT, Traits>&, char);
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&, char);

      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&, signed char);
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&, unsigned char);

      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&,
                                                wchar_t) = delete;
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&,
                                                char8_t) = delete;
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&,
                                                char16_t) = delete;
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&,
                                                char32_t) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, char8_t) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, char16_t) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, char32_t) = delete;

      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& operator<<(basic_ostream<CharT, Traits>&, const CharT*);
      template<class CharT, class Traits>
        basic_ostream<CharT, Traits>& operator<<(basic_ostream<CharT, Traits>&, const char*);
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&, const char*);

      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&,
                                                const signed char*);
      template<class Traits>
        basic_ostream<char, Traits>& operator<<(basic_ostream<char, Traits>&,
                                                const unsigned char*);

      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const wchar_t*) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const char8_t*) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const char16_t*) = delete;
      template<class Traits>
        basic_ostream<char, Traits>&
          operator<<(basic_ostream<char, Traits>&, const char32_t*) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, const char8_t*) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, const char16_t*) = delete;
      template<class Traits>
        basic_ostream<wchar_t, Traits>&
          operator<<(basic_ostream<wchar_t, Traits>&, const char32_t*) = delete;
    }

#### Class std::basic_ostream::sentry

    namespace std {
      template<class CharT, class Traits>
      class basic_ostream<CharT, Traits>::sentry {
        bool ok_;       // exposition only
      public:
        explicit sentry(basic_ostream& os);
        ~sentry();
        explicit operator bool() const { return ok_; }

        sentry(const sentry&) = delete;
        sentry& operator=(const sentry&) = delete;
      };
    }

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