Standard library header <iosfwd>

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library(C++20)

Diagnostics library

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)

Atomic operations library(C++11)

Thread support library(C++11)

Technical Specifications

 

Standard Library headers

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

 

This header contains forward declarations for the Input/output library.

Forward declarations
Defined in header <string>
std::char_traits	Class Template which describes properties of a character type (class template)
std::char_traits<char>	(class template specialization)
std::char_traits<wchar_t>	(class template specialization)
std::char_traits<char8_t>(C++20)	(class template specialization)
std::char_traits<char16_t>(C++11)	(class template specialization)
std::char_traits<char32_t>(C++11)	(class template specialization)
Defined in header <memory>
allocator	the default allocator (class template)
Defined in header <ios>
basic_ios	manages an arbitrary stream buffer (class template)
fpos	represents absolute position in a stream or a file (class template)
Defined in header <streambuf>
basic_streambuf	abstracts a raw device (class template)
Defined in header <ostream>
basic_ostream	wraps a given abstract device (std::basic_streambuf) and provides high-level output interface (class template)
Defined in header <istream>
basic_istream	wraps a given abstract device (std::basic_streambuf) and provides high-level input interface (class template)
basic_iostream	wraps a given abstract device (std::basic_streambuf) and provides high-level input/output interface (class template)
Defined in header <fstream>
basic_filebuf	implements raw file device (class template)
basic_ifstream	implements high-level file stream input operations (class template)
basic_ofstream	implements high-level file stream output operations (class template)
basic_fstream	implements high-level file stream input/output operations (class template)
Defined in header <sstream>
basic_stringbuf	implements raw string device (class template)
basic_istringstream	implements high-level string stream input operations (class template)
basic_ostringstream	implements high-level string stream output operations (class template)
basic_stringstream	implements high-level string stream input/output operations (class template)
Defined in header <syncstream>
basic_syncbuf (C++20)	synchronized output device wrapper (class template)
basic_osyncstream (C++20)	synchronized output stream wrapper (class template)
Defined in header <strstream>
strstreambuf (deprecated in C++98)	implements raw character array device (class)
istrstream (deprecated in C++98)	implements character array input operations (class)
ostrstream (deprecated in C++98)	implements character array output operations (class)
strstream (deprecated in C++98)	implements character array input/output operations (class)
Typedefs and specializations
std::streampos	std::fpos<std::char_traits<char>::state_type>
std::wstreampos	std::fpos<std::char_traits<wchar_t>::state_type>
std::u8streampos	std::fpos<std::char_traits<char8_t>::state_type>
std::u16streampos	std::fpos<std::char_traits<char16_t>::state_type>
std::u32streampos	std::fpos<std::char_traits<char32_t>::state_type>
In addition, for each class template std::basic_T declared in this header, std::T and std::wT are declared as a synonym of std::basic_T<char> and std::basic_T<wchar_t> respectively.

Synopsis

namespace std {template<class CharT>struct char_traits;template<>struct char_traits<char>;template<>struct char_traits<char8_t>;template<>struct char_traits<char16_t>;template<>struct char_traits<char32_t>;template<>struct char_traits<wchar_t>;   template<class T>class allocator;   template<class CharT, class Traits = char_traits<CharT>>class basic_ios;template<class CharT, class Traits = char_traits<CharT>>class basic_streambuf;template<class CharT, class Traits = char_traits<CharT>>class basic_istream;template<class CharT, class Traits = char_traits<CharT>>class basic_ostream;template<class CharT, class Traits = char_traits<CharT>>class basic_iostream;   template<class CharT, class Traits = char_traits<CharT>>class Allocator = allocator<CharT>>class basic_stringbuf;template<class CharT, class Traits = char_traits<CharT>>class Allocator = allocator<CharT>>class basic_istringstream;template<class CharT, class Traits = char_traits<CharT>>class Allocator = allocator<CharT>>class basic_ostringstream;template<class CharT, class Traits = char_traits<CharT>>class Allocator = allocator<CharT>>class basic_stringstream;   template<class CharT, class Traits = char_traits<CharT>>class basic_filebuf;template<class CharT, class Traits = char_traits<CharT>>class basic_ifstream;template<class CharT, class Traits = char_traits<CharT>>class basic_ofstream;template<class CharT, class Traits = char_traits<CharT>>class basic_fstream;   template<class CharT, class Traits = char_traits<CharT>>class Allocator = allocator<CharT>>class basic_syncbuf;template<class CharT, class Traits = char_traits<CharT>>class Allocator = allocator<CharT>>class basic_osyncstream;   template<class CharT, class Traits = char_traits<CharT>>class istreambuf_iterator;template<class CharT, class Traits = char_traits<CharT>>class ostreambuf_iterator;   using ios = basic_ios<char>;using wios = basic_ios<wchar_t>;   using streambuf = basic_streambuf<char>;using istream = basic_istream<char>;using ostream = basic_ostream<char>;using iostream = basic_iostream<char>;   using stringbuf = basic_stringbuf<char>;using istringstream = basic_istringstream<char>;using ostringstream = basic_ostringstream<char>;using stringstream = basic_stringstream<char>;   using filebuf = basic_filebuf<char>;using ifstream = basic_ifstream<char>;using ofstream = basic_ofstream<char>;using fstream = basic_fstream<char>;   using syncbuf = basic_syncbuf<char>;using osyncstream = basic_osyncstream<char>;   using wstreambuf = basic_streambuf<wchar_t>;using wistream = basic_istream<wchar_t>;using wostream = basic_ostream<wchar_t>;using wiostream = basic_iostream<wchar_t>;   using wstringbuf = basic_stringbuf<wchar_t>;using wistringstream = basic_istringstream<wchar_t>;using wostringstream = basic_ostringstream<wchar_t>;using wstringstream = basic_stringstream<wchar_t>;   using wfilebuf = basic_filebuf<wchar_t>;using wifstream = basic_ifstream<wchar_t>;using wofstream = basic_ofstream<wchar_t>;using wfstream = basic_fstream<wchar_t>;   using wsyncbuf = basic_syncbuf<wchar_t>;using wosyncstream = basic_osyncstream<wchar_t>;   template<class State>class fpos;using streampos = fpos<char_traits<char>::state_type>;using wstreampos = fpos<char_traits<wchar_t>::state_type>;using u8streampos = fpos<char_traits<char8_t>::state_type>;using u16streampos = fpos<char_traits<char16_t>::state_type>;using u32streampos = fpos<char_traits<char32_t>::state_type>;}   // deprecatednamespace std {class strstreambuf;class istrstream;class ostrstream;class strstream;}