27 Input/output library [input.output]

27.7 Formatting and manipulators [iostream.format]

27.7.3 Output streams [output.streams]

27.7.3.1 Class template basic_ostream [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 ([ios])):
    typedef charT                     char_type;
    typedef typename traits::int_type int_type;
    typedef typename traits::pos_type pos_type;
    typedef typename traits::off_type off_type;
    typedef traits                    traits_type;

    // [ostream.cons] Constructor/destructor:
    explicit basic_ostream(basic_streambuf<char_type,traits>* sb);
    virtual ~basic_ostream();

    // [ostream::sentry] Prefix/suffix:
    class sentry;

    // [ostream.formatted] Formatted output:
    basic_ostream<charT,traits>& operator<<(
      basic_ostream<charT,traits>& (*pf)(basic_ostream<charT,traits>&));
    basic_ostream<charT,traits>& operator<<(
      basic_ios<charT,traits>& (*pf)(basic_ios<charT,traits>&));
    basic_ostream<charT,traits>& operator<<(
      ios_base& (*pf)(ios_base&));

    basic_ostream<charT,traits>& operator<<(bool n);
    basic_ostream<charT,traits>& operator<<(short n);
    basic_ostream<charT,traits>& operator<<(unsigned short n);
    basic_ostream<charT,traits>& operator<<(int n);
    basic_ostream<charT,traits>& operator<<(unsigned int n);
    basic_ostream<charT,traits>& operator<<(long n);
    basic_ostream<charT,traits>& operator<<(unsigned long n);
    basic_ostream<charT,traits>& operator<<(long long n);
    basic_ostream<charT,traits>& operator<<(unsigned long long n);
    basic_ostream<charT,traits>& operator<<(float f);
    basic_ostream<charT,traits>& operator<<(double f);
    basic_ostream<charT,traits>& operator<<(long double f);

    basic_ostream<charT,traits>& operator<<(const void* p);
    basic_ostream<charT,traits>& operator<<(
      basic_streambuf<char_type,traits>* sb);

    // [ostream.unformatted] Unformatted output:
    basic_ostream<charT,traits>& put(char_type c);
    basic_ostream<charT,traits>& write(const char_type* s, streamsize n);

    basic_ostream<charT,traits>& flush();

    // [ostream.seeks] seeks:
    pos_type tellp();
    basic_ostream<charT,traits>& seekp(pos_type);
    basic_ostream<charT,traits>& seekp(off_type, ios_base::seekdir);
  protected:
    basic_ostream(const basic_ostream& rhs) = delete;
    basic_ostream(basic_ostream&& rhs);

    // [ostream.assign] Assign/swap
    basic_ostream& operator=(const basic_ostream& rhs) = delete;
    basic_ostream& operator=(basic_ostream&& rhs);
    void swap(basic_ostream& rhs);
  };

  // [ostream.inserters.character] 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);

  // signed and unsigned
  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 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*);

  // signed and unsigned
  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*);
}

The class basic_ostream defines a number of member function signatures that assist in formatting and writing output to output sequences controlled by a stream buffer.

Two groups of member function signatures share common properties: the formatted output functions (or inserters) and the unformatted output functions. Both groups of output functions generate (or insert) output characters by actions equivalent to calling rdbuf()->sputc(int_type). They may use other public members of basic_ostream except that they shall not invoke any virtual members of rdbuf() except overflow(), xsputn(), and sync().

If one of these called functions throws an exception, then unless explicitly noted otherwise the output function sets badbit in error state. If badbit is on in exceptions(), the output function rethrows the exception without completing its actions, otherwise it does not throw anything and treat as an error.