# Standard library header <istream>

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< cpp‎ | header

This header is part of the input/output library.

### Classes

basic_istream | wraps a given abstract device (std::basic_streambuf) and provides high-level input interface (class template)
std::istream | std::basic_istream <char> (typedef)
std::wistream | std::basic_istream <wchar_t> (typedef)
basic_iostream | wraps a given abstract device (std::basic_streambuf) and provides high-level input/output interface (class template)
std::iostream | std::basic_iostream <char> (typedef)
std::wiostream | std::basic_iostream <wchar_t> (typedef)

### Functions

operator>>(std::basic_istream) | extracts characters and character arrays (function template)

##### Manipulators

ws | consumes whitespace (function template)

### Synopsis

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

      using istream  = basic_istream<char>;
      using wistream = basic_istream<wchar_t>;

      template<class CharT, class Traits = char_traits<CharT>>
        class basic_iostream;

      using iostream  = basic_iostream<char>;
      using wiostream = basic_iostream<wchar_t>;

      template<class CharT, class Traits>
        basic_istream<CharT, Traits>& ws(basic_istream<CharT, Traits>& is);

      template<class Istream, class T>
        Istream&& operator>>(Istream&& is, T&& x);
    }

#### Class template std::basic_istream

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
      class basic_istream : 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_istream(basic_streambuf<CharT, Traits>* sb);
        virtual ~basic_istream();

        // prefix/suffix
        class sentry;

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

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

        basic_istream& operator>>(void*& p);
        basic_istream& operator>>(basic_streambuf<char_type, Traits>* sb);

        // unformatted input
        streamsize gcount() const;
        int_type get();
        basic_istream& get(char_type& c);
        basic_istream& get(char_type* s, streamsize n);
        basic_istream& get(char_type* s, streamsize n, char_type delim);
        basic_istream& get(basic_streambuf<char_type, Traits>& sb);
        basic_istream& get(basic_streambuf<char_type, Traits>& sb, char_type delim);

        basic_istream& getline(char_type* s, streamsize n);
        basic_istream& getline(char_type* s, streamsize n, char_type delim);

        basic_istream& ignore(streamsize n = 1, int_type delim = Traits::eof());
        int_type       peek();
        basic_istream& read    (char_type* s, streamsize n);
        streamsize     readsome(char_type* s, streamsize n);

        basic_istream& putback(char_type c);
        basic_istream& unget();
        int sync();

        pos_type tellg();
        basic_istream& seekg(pos_type);
        basic_istream& seekg(off_type, ios_base::seekdir);

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

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

      // character extraction templates
      template<class CharT, class Traits>
        basic_istream<CharT, Traits>& operator>>(basic_istream<CharT, Traits>&, CharT&);
      template<class Traits>
        basic_istream<char, Traits>& operator>>(basic_istream<char, Traits>&, unsigned char&);
      template<class Traits>
        basic_istream<char, Traits>& operator>>(basic_istream<char, Traits>&, signed char&);

      template<class CharT, class Traits, size_t N>
        basic_istream<CharT, Traits>& operator>>(basic_istream<CharT, Traits>&, CharT(&)[N]);
      template<class Traits, size_t N>
        basic_istream<char, Traits>& operator>>(basic_istream<char, Traits>&, unsigned char(&)[N]);
      template<class Traits, size_t N>
        basic_istream<char, Traits>& operator>>(basic_istream<char, Traits>&, signed char(&)[N]);
    }

#### Class std::basic_istream::sentry

    namespace std {
      template<class CharT, class Traits>
      class basic_istream<CharT, Traits>::sentry {
        bool ok_;                   // exposition only
      public:
        explicit sentry(basic_istream& is, bool noskipws = false);
        ~sentry();
        explicit operator bool() const { return ok_; }
        sentry(const sentry&) = delete;
        sentry& operator=(const sentry&) = delete;
      };
    }

#### Class template std::basic_iostream

    namespace std {
      template<class CharT, class Traits = char_traits<CharT>>
      class basic_iostream
        : public basic_istream<CharT, Traits>,
          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;

        // constructor
        explicit basic_iostream(basic_streambuf<CharT, Traits>* sb);

        // destructor
        virtual ~basic_iostream();

      protected:
        // constructor
        basic_iostream(const basic_iostream&) = delete;
        basic_iostream(basic_iostream&& rhs);

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

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