Standard library header <istream>

 

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Standard library headers

Language support <cfloat> <climits> <compare> (C++20) <coroutine> (C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint> (C++11) <cstdlib> <exception> <initializer_list> (C++11)    <limits> <new> <source_location> (C++20) <stdfloat> (C++23) <typeinfo> <version> (C++20) Concepts <concepts> (C++20) Diagnostics <cassert> <cerrno> <debugging> (C++26) <stacktrace> (C++23) <stdexcept> <system_error> (C++11) Memory management <memory> <memory_resource> (C++17) <scoped_allocator> (C++11) Metaprogramming <type_traits> (C++11) <ratio> (C++11)

General utilities <any> (C++17) <bitset> <bit> (C++20) <charconv> (C++17) <expected> (C++23) <format> (C++20) <functional> <optional> (C++17) <tuple> (C++11) <typeindex> (C++11) <utility> <variant> (C++17) Containers <array> (C++11) <deque> <flat_map> (C++23) <flat_set> (C++23) <forward_list> (C++11) <inplace_vector> (C++26)    <list> <map> <mdspan> (C++23) <queue> <set> <span> (C++20) <stack> <unordered_map> (C++11) <unordered_set> (C++11) <vector> Iterators <iterator> Ranges <generator> (C++23) <ranges> (C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar> (C++11) <cwchar> <cwctype> <string_view> (C++17) <string> Text processing <clocale> <codecvt> (C++11/17/26*) <locale> <regex> (C++11) <text_encoding> (C++26)    Numerics <cfenv> (C++11) <cmath> <complex> <linalg> (C++26) <numbers> (C++20) <random> (C++11) <valarray> Time <chrono> (C++11) <ctime> C compatibility <ccomplex> (C++11/17/20*) <ciso646> (until C++20) <cstdalign> (C++11/17/20*) <cstdbool> (C++11/17/20*) <ctgmath> (C++11/17/20*)

Input/output <cinttypes> (C++11) <cstdio> <filesystem> (C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print> (C++23) <spanstream> (C++23) <sstream> <streambuf> <strstream> (C++98/26*) <syncstream> (C++20) Concurrency support <atomic> (C++11) <barrier> (C++20) <condition_variable> (C++11) <future> (C++11) <hazard_pointer> (C++26) <latch> (C++20) <mutex> (C++11) <rcu> (C++26) <semaphore> (C++20) <shared_mutex> (C++14) <stdatomic.h> (C++23) <stop_token> (C++20) <thread> (C++11) Execution support <execution> (C++17)

 

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);
  };
}