Standard library header <ostream>

 

C++

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Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Standard library headers

Language support
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <stdfloat> (C++23) <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> <stacktrace> (C++23)	<cassert>	<cerrno>	<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
<utility> <tuple> (C++11) <optional> (C++17) <variant> (C++17)	<any> (C++17) <expected> (C++23) <bitset>	<functional> <typeindex> (C++11) <execution> (C++17)	<charconv> (C++17) <format> (C++20) <bit> (C++20)
Strings
<string_view> (C++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (C++11)
Containers
<array> (C++11) <deque> <forward_list> (C++11) <list>	<vector> <map> <set> <unordered_map> (C++11)	<unordered_set> (C++11) <queue> <stack> <flat_map> (C++23)	<flat_set> (C++23) <span> (C++20) <mdspan> (C++23)
Iterators
<iterator>
Ranges
<ranges> (C++20)	<generator> (C++23)
Algorithms
<algorithm>	<numeric>
Numerics
<cfenv> (C++11) <complex>	<random> (C++11) <valarray>	<cmath>	<numbers> (C++20)
Time
<chrono> (C++11)	<ctime>
Localization
<locale>	<clocale>	<codecvt> (C++11/17*)
Input/output
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (C++23)	<sstream> <spanstream> (C++23) <fstream> <syncstream> (C++20)	<filesystem> (C++17) <cstdio> <cinttypes> (C++11) <strstream> (C++98*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20) <thread> (C++11) <atomic> (C++11)	<stdatomic.h> (C++23) <mutex> (C++11) <shared_mutex> (C++14)	<condition_variable> (C++11)   <semaphore> (C++20) <latch> (C++20)	<barrier> (C++20) <future> (C++11)
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)

 

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_flushnoemit_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;
  };
}