std::basic_iostream

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

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)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Input/output library

I/O manipulators

Print functions (C++23)

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

basic_spanbuf (C++23)

strstreambuf (C++98/26*)

basic_syncbuf (C++20)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

basic_ispanstream (C++23)

basic_ospanstream (C++23)

basic_spanstream (C++23)

istrstream (C++98/26*)

ostrstream (C++98/26*)

strstream (C++98/26*)

Synchronized Output

basic_osyncstream (C++20)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

std::basic_iostream

Member functions

basic_iostream::basic_iostream

basic_iostream::~basic_iostream

Protected member functions

basic_iostream::operator=

basic_iostream::swap

 

Defined in header <istream>
template<     class CharT,     class Traits = std::char_traits<CharT> > class basic_iostream :       public basic_istream<CharT, Traits>,       public basic_ostream<CharT, Traits>

The class template basic_iostream provides support for high level input/output operations on streams. The supported operations include sequential reading or writing and formatting. This functionality is implemented over the interface provided by the std::basic_streambuf class. It is accessed through std::basic_ios class.

Inheritance diagram

Several typedefs for common character types are provided:

Defined in header <istream>
Type	Definition
std::iostream	std::basic_iostream<char>
std::wiostream	std::basic_iostream<wchar_t>

Member types

Member type	Definition
char_type	CharT
traits_type	Traits; the program is ill-formed if Traits::char_type is not CharT.
int_type	Traits::int_type
pos_type	Traits::pos_type
off_type	Traits::off_type

Member functions

(constructor)	constructs the object (public member function)
(destructor) [virtual]	destructs the object (virtual public member function)

Protected member functions

operator= (C++11)	move-assigns another basic_iostream (protected member function)
swap (C++11)	exchanges the state with another basic_iostream (public member function)

Inherited from std::basic_istream

Member functions

Formatted input
operator>>	extracts formatted data (public member function of std::basic_istream<CharT,Traits>)
Unformatted input
get	extracts characters (public member function of std::basic_istream<CharT,Traits>)
peek	reads the next character without extracting it (public member function of std::basic_istream<CharT,Traits>)
unget	unextracts a character (public member function of std::basic_istream<CharT,Traits>)
putback	puts a character into input stream (public member function of std::basic_istream<CharT,Traits>)
getline	extracts characters until the given character is found (public member function of std::basic_istream<CharT,Traits>)
ignore	extracts and discards characters until the given character is found (public member function of std::basic_istream<CharT,Traits>)
read	extracts blocks of characters (public member function of std::basic_istream<CharT,Traits>)
readsome	extracts already available blocks of characters (public member function of std::basic_istream<CharT,Traits>)
gcount	returns number of characters extracted by last unformatted input operation (public member function of std::basic_istream<CharT,Traits>)
Positioning
tellg	returns the input position indicator (public member function of std::basic_istream<CharT,Traits>)
seekg	sets the input position indicator (public member function of std::basic_istream<CharT,Traits>)
Miscellaneous
sync	synchronizes with the underlying storage device (public member function of std::basic_istream<CharT,Traits>)

Member classes

sentry

implements basic logic for preparation of the stream for input operations (public member class of std::basic_istream<CharT,Traits>)

Inherited from std::basic_ostream

Member functions

Formatted output
operator<<	inserts formatted data (public member function of std::basic_ostream<CharT,Traits>)
Unformatted output
put	inserts a character (public member function of std::basic_ostream<CharT,Traits>)
write	inserts blocks of characters (public member function of std::basic_ostream<CharT,Traits>)
Positioning
tellp	returns the output position indicator (public member function of std::basic_ostream<CharT,Traits>)
seekp	sets the output position indicator (public member function of std::basic_ostream<CharT,Traits>)
Miscellaneous
flush	synchronizes with the underlying storage device (public member function of std::basic_ostream<CharT,Traits>)

Member classes

sentry

implements basic logic for preparation of the stream for output operations (public member class of std::basic_ostream<CharT,Traits>)

Inherited from std::basic_ios

Member types

Member type	Definition
char_type	CharT
traits_type	Traits
int_type	Traits::int_type
pos_type	Traits::pos_type
off_type	Traits::off_type

Member functions

State functions
good	checks if no error has occurred i.e. I/O operations are available (public member function of std::basic_ios<CharT,Traits>)
eof	checks if end-of-file has been reached (public member function of std::basic_ios<CharT,Traits>)
fail	checks if an error has occurred (public member function of std::basic_ios<CharT,Traits>)
bad	checks if a non-recoverable error has occurred (public member function of std::basic_ios<CharT,Traits>)
operator!	checks if an error has occurred (synonym of fail()) (public member function of std::basic_ios<CharT,Traits>)
operator bool	checks if no error has occurred (synonym of !fail()) (public member function of std::basic_ios<CharT,Traits>)
rdstate	returns state flags (public member function of std::basic_ios<CharT,Traits>)
setstate	sets state flags (public member function of std::basic_ios<CharT,Traits>)
clear	modifies state flags (public member function of std::basic_ios<CharT,Traits>)
Formatting
copyfmt	copies formatting information (public member function of std::basic_ios<CharT,Traits>)
fill	manages the fill character (public member function of std::basic_ios<CharT,Traits>)
Miscellaneous
exceptions	manages exception mask (public member function of std::basic_ios<CharT,Traits>)
imbue	sets the locale (public member function of std::basic_ios<CharT,Traits>)
rdbuf	manages associated stream buffer (public member function of std::basic_ios<CharT,Traits>)
tie	manages tied stream (public member function of std::basic_ios<CharT,Traits>)
narrow	narrows characters (public member function of std::basic_ios<CharT,Traits>)
widen	widens characters (public member function of std::basic_ios<CharT,Traits>)

Inherited from std::ios_base

Member functions

Formatting
flags	manages format flags (public member function of std::ios_base)
setf	sets specific format flag (public member function of std::ios_base)
unsetf	clears specific format flag (public member function of std::ios_base)
precision	manages decimal precision of floating point operations (public member function of std::ios_base)
width	manages field width (public member function of std::ios_base)
Locales
imbue	sets locale (public member function of std::ios_base)
getloc	returns current locale (public member function of std::ios_base)
Internal extensible array
xalloc [static]	returns a program-wide unique integer that is safe to use as index to pword() and iword() (public static member function of std::ios_base)
iword	resizes the private storage if necessary and access to the long element at the given index (public member function of std::ios_base)
pword	resizes the private storage if necessary and access to the void* element at the given index (public member function of std::ios_base)
Miscellaneous
register_callback	registers event callback function (public member function of std::ios_base)
sync_with_stdio [static]	sets whether C++ and C I/O libraries are interoperable (public static member function of std::ios_base)
Member classes
failure	stream exception (public member class of std::ios_base)
Init	initializes standard stream objects (public member class of std::ios_base)

Member types and constants
Type	Explanation
openmode	stream open mode type The following constants are also defined: Constant Explanation app seek to the end of stream before each write binary open in binary mode in open for reading out open for writing trunc discard the contents of the stream when opening ate seek to the end of stream immediately after open noreplace (C++23) open in exclusive mode (typedef)
fmtflags	formatting flags type The following constants are also defined: Constant Explanation dec use decimal base for integer I/O: see std::dec oct use octal base for integer I/O: see std::oct hex use hexadecimal base for integer I/O: see std::hex basefield dec | oct | hex. Useful for masking operations left left adjustment (adds fill characters to the right): see std::left right right adjustment (adds fill characters to the left): see std::right internal internal adjustment (adds fill characters to the internal designated point): see std::internal adjustfield left | right | internal. Useful for masking operations scientific generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific fixed generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed floatfield scientific | fixed. Useful for masking operations boolalpha insert and extract bool type in alphanumeric format: see std::boolalpha showbase generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase showpoint generate a decimal-point character unconditionally for floating-point number output: see std::showpoint showpos generate a + character for non-negative numeric output: see std::showpos skipws skip leading whitespace before certain input operations: see std::skipws unitbuf flush the output after each output operation: see std::unitbuf uppercase replace certain lowercase letters with their uppercase equivalents in certain output operations: see std::uppercase (typedef)
iostate	state of the stream type The following constants are also defined: Constant Explanation goodbit no error badbit irrecoverable stream error failbit input/output operation failed (formatting or extraction error) eofbit associated input sequence has reached end-of-file (typedef)
seekdir	seeking direction type The following constants are also defined: Constant Explanation beg the beginning of a stream end the ending of a stream cur the current position of stream position indicator (typedef)
event	specifies event type (enum)
event_callback	callback function type (typedef)

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 271	C++98	the member types char_type, traits_type, int_type, pos_type and off_type were not defined (std::basic_istream and std::basic_ostream both define these types, resulted in ambiguity)	define these types

See also

• Input/output manipulators