C++ includes the following input/output libraries: an
library,
of functions(since C++23), and the standard set of
functions.
Stream-based I/O
The stream-based input/output library is organized around abstract input/output devices. These abstract devices allow the same code to handle input/output to files, memory streams, or custom adaptor devices that perform arbitrary operations (e.g. compression) on the fly.
Most of the classes are templated, so they can be adapted to any basic character type. Separate typedefs are provided for the most common basic character types (char and wchar_t). The classes are organized into the following hierarchy:
Inheritance diagram
Abstraction Defined in header
manages formatting flags and input/output exceptions
(class)
manages an arbitrary stream buffer
(class template)
Defined in header
abstracts a raw device
(class template)
Defined in header
wraps a given abstract device (
)
and provides high-level output interface
(class template)
Defined in header
wraps a given abstract device (
)
and provides high-level input interface
(class template)
wraps a given abstract device (
)
and provides high-level input/output interface
(class template)
File I/O implementation Defined in header
implements raw file device
(class template)
implements high-level file stream input operations
(class template)
implements high-level file stream output operations
(class template)
implements high-level file stream input/output operations
(class template)
String I/O implementation Defined in header
implements raw string device
(class template)
implements high-level string stream input operations
(class template)
implements high-level string stream output operations
(class template)
implements high-level string stream input/output operations
(class template)
Array I/O implementations Defined in header
(C++23)
implements raw fixed character buffer device
(class template)
(C++23)
implements fixed character buffer input operations
(class template)
(C++23)
implements fixed character buffer output operations
(class template)
(C++23)
implements fixed character buffer input/output operations
(class template)
Defined in header
(deprecated in C++98)(removed in C++26)
implements raw character array device
(class)
(deprecated in C++98)(removed in C++26)
implements character array input operations
(class)
(deprecated in C++98)(removed in C++26)
implements character array output operations
(class)
(deprecated in C++98)(removed in C++26)
implements character array input/output operations
(class)
Synchronized output (since C++20)Defined in header
(C++20)
synchronized output device wrapper
(class template)
(C++20)
synchronized output stream wrapper
(class template)
Typedefs
The following typedefs for common character types are provided in namespace std:
Type Definition Defined in header
std::iosstd::basic_ios<char>std::wiosstd::basic_ios<wchar_t>Defined in header
std::basic_streambuf<char>
std::basic_streambuf<wchar_t>Defined in header
std::basic_istream<char>
std::basic_istream<wchar_t>
std::basic_iostream<char>
std::basic_iostream<wchar_t>Defined in header
std::basic_ostream<char>
std::basic_ostream<wchar_t>Defined in header
std::basic_filebuf<char>
std::basic_filebuf<wchar_t>
std::basic_ifstream<char>
std::basic_ifstream<wchar_t>
std::basic_ofstream<char>
std::basic_ofstream<wchar_t>
std::basic_fstream<char>
std::basic_fstream<wchar_t>Defined in header
std::basic_stringbuf<char>
std::basic_stringbuf<wchar_t>
std::basic_istringstream<char>
std::basic_istringstream<wchar_t>
std::basic_ostringstream<char>
std::basic_ostringstream<wchar_t>
std::basic_stringstream<char>
std::basic_stringstream<wchar_t>Defined in header
std::spanbuf(C++23)std::basic_spanbuf<char>std::wspanbuf(C++23)std::basic_spanbuf<wchar_t>std::ispanstream(C++23)std::basic_ispanstream<char>std::wispanstream(C++23)std::basic_ispanstream<wchar_t>std::ospanstream(C++23)std::basic_ospanstream<char>std::wospanstream(C++23)std::basic_ospanstream<wchar_t>std::spanstream(C++23)std::basic_spanstream<char>std::wspanstream(C++23)std::basic_spanstream<wchar_t>Defined in header
std::syncbuf(C++20)std::basic_syncbuf<char>std::wsyncbuf(C++20)std::basic_syncbuf<wchar_t>std::osyncstream(C++20)std::basic_osyncstream<char>std::wosyncstream(C++20)std::basic_osyncstream<wchar_t>Predefined standard stream objects
The stream-based I/O library uses
(e.g.
,
, etc.) to control how streams behave.
Types
The following auxiliary types are defined:
Defined in header
represents relative file/stream position (offset from fpos), sufficient to represent any file size
(typedef)
represents the number of characters transferred in an I/O operation or the size of an I/O buffer
(typedef)
represents absolute position in a stream or a file
(class template)
The following typedef names for std::fpos<std::mbstate_t> are provided:
Defined in header
Type Definition std::streamposstd::fpos<std::char_traits<char>::state_type>std::wstreamposstd::fpos<std::char_traits<wchar_t>::state_type>std::u8streampos(C++20)std::fpos<std::char_traits<char8_t>::state_type>std::u16streampos(C++11)std::fpos<std::char_traits<char16_t>::state_type>std::u32streampos(C++11)std::fpos<std::char_traits<char32_t>::state_type>Error category interface (since C++11)
Print functions (since C++23)
The Unicode-aware print-family functions that perform formatted I/O on text that is already formatted. They bring all the performance benefits of
, are locale-independent by default, reduce global state, avoid allocating a temporary
object and calling operator<<, and in general make formatting more efficient compared to
and
.
The following print-like functions are provided:
Defined in header
(C++23)
prints to
or a file stream using
representation of the arguments
(function template)
(C++23)
same as std::print except that each print is terminated by additional new line
(function template)
vprint_unicodevprint_unicode_buffered
(C++23)
prints to Unicode capable
or a file stream using
argument representation
(function)
vprint_nonunicodevprint_nonunicode_buffered
(C++23)
prints to
or a file stream using
argument representation
(function)
Defined in header
(C++23)
outputs
representation of the arguments
(function template)
(C++23)
outputs
representation of the arguments with appended '\n'
(function template)
C++ also includes the
input/output functions defined by C
, such as
,
, etc.
See also