Standard library header <istream>

 

C++

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Ranges library (C++20)

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Standard Library headers

Note: a slash '/' in a revision mark means that the header was deprecated and/or removed.

Language Support
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <new> <typeinfo>	<source_location> (C++20) <exception> <initializer_list> (C++11)   <compare> (C++20)	<coroutine> (C++20) <csignal> <csetjmp> <cstdarg>
Concepts
<concepts> (C++20)
Diagnostics
<stdexcept>	<cassert>	<cerrno>	<system_error> (C++11)
General utilities
<utility> <memory> <memory_resource> (C++17) <scoped_allocator> (C++11)   <expected> (C++23)	<bitset> <tuple> (C++11) <optional> (C++17) <any> (C++17)	<variant> (C++17) <type_traits> (C++11) <ratio> (C++11) <chrono> (C++11)	<typeindex> (C++11) <functional> <stacktrace> (C++23) <ctime>
Strings
<string> <string_view> (C++17) <cstring>	<charconv> (C++17) <format> (C++20)	<cctype> <cwctype>	<cwchar> <cuchar> (C++11)
Localization
<locale> <clocale>	<codecvt> (C++11/17)
Containers
<span> (C++20) <array> (C++11) <vector>	<deque> <forward_list> (C++11) <list>	<map> <set> <queue>	<unordered_map> (C++11) <unordered_set> (C++11) <stack>
Iterators
<iterator>
Ranges
<ranges> (C++20)
Algorithms
<algorithm>	<execution> (C++17)
Numerics
<complex> <random> (C++11)	<valarray> <numeric>	<bit> (C++20) <numbers> (C++20)	<cfenv> (C++11) <cmath>
Input/Output
<iosfwd> <ios> <iomanip> <streambuf>	<istream> <ostream> <iostream>	<syncstream> (C++20) <spanstream> (C++23) <sstream> <fstream>	<cstdio> <cinttypes> (C++11) <strstream> (C++98/)
Regular expressions
<regex> (C++11)
Filesystem support
<filesystem> (C++17)
Thread support
<thread> (C++11) <atomic> (C++11) <mutex> (C++11)	<shared_mutex> (C++14) <condition_variable> (C++11)   <future> (C++11)	<stop_token> (C++20) <semaphore> (C++20)	<latch> (C++20) <barrier> (C++20)
C compatibility
<cstdbool> (C++11/17/20) <ccomplex> (C++11/17/20)	<ctgmath> (C++11/17/20) <cstdalign> (C++11/17/20)	<ciso646> (until C++20) <stdatomic.h>

 

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<CharT, Traits>&
      operator>>(basic_istream<CharT, Traits>& (*pf)(basic_istream<CharT, Traits>&));
    basic_istream<CharT, Traits>&
      operator>>(basic_ios<CharT, Traits>& (*pf)(basic_ios<CharT, Traits>&));
    basic_istream<CharT, Traits>&
      operator>>(ios_base& (*pf)(ios_base&));
 
    basic_istream<CharT, Traits>& operator>>(bool& n);
    basic_istream<CharT, Traits>& operator>>(short& n);
    basic_istream<CharT, Traits>& operator>>(unsigned short& n);
    basic_istream<CharT, Traits>& operator>>(int& n);
    basic_istream<CharT, Traits>& operator>>(unsigned int& n);
    basic_istream<CharT, Traits>& operator>>(long& n);
    basic_istream<CharT, Traits>& operator>>(unsigned long& n);
    basic_istream<CharT, Traits>& operator>>(long long& n);
    basic_istream<CharT, Traits>& operator>>(unsigned long long& n);
    basic_istream<CharT, Traits>& operator>>(float& f);
    basic_istream<CharT, Traits>& operator>>(double& f);
    basic_istream<CharT, Traits>& operator>>(long double& f);
 
    basic_istream<CharT, Traits>& operator>>(void*& p);
    basic_istream<CharT, Traits>& operator>>(basic_streambuf<char_type, Traits>* sb);
 
    // unformatted input
    streamsize gcount() const;
    int_type get();
    basic_istream<CharT, Traits>& get(char_type& c);
    basic_istream<CharT, Traits>& get(char_type* s, streamsize n);
    basic_istream<CharT, Traits>& get(char_type* s, streamsize n, char_type delim);
    basic_istream<CharT, Traits>& get(basic_streambuf<char_type, Traits>& sb);
    basic_istream<CharT, Traits>&
      get(basic_streambuf<char_type, Traits>& sb, char_type delim);
 
    basic_istream<CharT, Traits>& getline(char_type* s, streamsize n);
    basic_istream<CharT, Traits>& getline(char_type* s, streamsize n, char_type delim);
 
    basic_istream<CharT, Traits>& ignore(streamsize n = 1, int_type delim = Traits::eof());
    int_type                      peek();
    basic_istream<CharT, Traits>& read    (char_type* s, streamsize n);
    streamsize                    readsome(char_type* s, streamsize n);
 
    basic_istream<CharT, Traits>& putback(char_type c);
    basic_istream<CharT, Traits>& unget();
    int sync();
 
    pos_type tellg();
    basic_istream<CharT, Traits>& seekg(pos_type);
    basic_istream<CharT, Traits>& seekg(off_type, ios_base::seekdir);
 
  protected:
    // copy/move constructor
    basic_istream(const basic_istream&) = delete;
    basic_istream(basic_istream&& rhs);
 
    // assign 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 = char_traits<CharT>>
  class basic_istream<CharT, Traits>::sentry {
    bool ok_;                   // exposition only
  public:
    explicit sentry(basic_istream<CharT, Traits>& 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);
 
    // assign and swap
    basic_iostream& operator=(const basic_iostream&) = delete;
    basic_iostream& operator=(basic_iostream&& rhs);
    void swap(basic_iostream& rhs);
  };
}