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std::basic_iostream - cppreference.com

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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.

cpp/io/ios basecpp/io/basic ioscpp/io/basic istreamcpp/io/basic ostream

Inheritance diagram

Several typedefs for common character types are provided:

Type Definition
std::iostream std::basic_iostream<char>
std::wiostream std::basic_iostream<wchar_t>

Member types

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

Member functions

Protected member functions

move-assigns another basic_iostream
(protected member function) [edit]
exchanges the state with another basic_iostream
(public member function) [edit]

Inherited from std::basic_istream

Member functions

Formatted input
extracts formatted data
(public member function of std::basic_istream<CharT,Traits>) [edit]
Unformatted input
extracts characters
(public member function of std::basic_istream<CharT,Traits>) [edit]
reads the next character without extracting it
(public member function of std::basic_istream<CharT,Traits>) [edit]
unextracts a character
(public member function of std::basic_istream<CharT,Traits>) [edit]
puts a character into input stream
(public member function of std::basic_istream<CharT,Traits>) [edit]
extracts characters until the given character is found
(public member function of std::basic_istream<CharT,Traits>) [edit]
extracts and discards characters until the given character is found
(public member function of std::basic_istream<CharT,Traits>) [edit]
extracts blocks of characters
(public member function of std::basic_istream<CharT,Traits>) [edit]
extracts already available blocks of characters
(public member function of std::basic_istream<CharT,Traits>) [edit]
returns number of characters extracted by last unformatted input operation
(public member function of std::basic_istream<CharT,Traits>) [edit]
Positioning
returns the input position indicator
(public member function of std::basic_istream<CharT,Traits>) [edit]
sets the input position indicator
(public member function of std::basic_istream<CharT,Traits>) [edit]
Miscellaneous
synchronizes with the underlying storage device
(public member function of std::basic_istream<CharT,Traits>) [edit]

Member classes

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

Inherited from std::basic_ostream

Member functions

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

Member classes

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

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
checks if no error has occurred i.e. I/O operations are available
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if end-of-file has been reached
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if an error has occurred
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if a non-recoverable error has occurred
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if an error has occurred (synonym of std::basic_ios::fail)
(public member function of std::basic_ios<CharT,Traits>) [edit]
checks if no error has occurred (synonym of !std::basic_ios::fail)
(public member function of std::basic_ios<CharT,Traits>) [edit]
returns state flags
(public member function of std::basic_ios<CharT,Traits>) [edit]
sets state flags
(public member function of std::basic_ios<CharT,Traits>) [edit]
modifies state flags
(public member function of std::basic_ios<CharT,Traits>) [edit]
Formatting
copies formatting information
(public member function of std::basic_ios<CharT,Traits>) [edit]
manages the fill character
(public member function of std::basic_ios<CharT,Traits>) [edit]
Miscellaneous
manages exception mask
(public member function of std::basic_ios<CharT,Traits>) [edit]
sets the locale
(public member function of std::basic_ios<CharT,Traits>) [edit]
manages associated stream buffer
(public member function of std::basic_ios<CharT,Traits>) [edit]
manages tied stream
(public member function of std::basic_ios<CharT,Traits>) [edit]
narrows characters
(public member function of std::basic_ios<CharT,Traits>) [edit]
widens characters
(public member function of std::basic_ios<CharT,Traits>) [edit]

Inherited from std::ios_base

Member functions

Formatting
manages format flags
(public member function of std::ios_base) [edit]
sets specific format flag
(public member function of std::ios_base) [edit]
clears specific format flag
(public member function of std::ios_base) [edit]
manages decimal precision of floating point operations
(public member function of std::ios_base) [edit]
manages field width
(public member function of std::ios_base) [edit]
Locales
sets locale
(public member function of std::ios_base) [edit]
returns current locale
(public member function of std::ios_base) [edit]
Internal extensible array

[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) [edit]
resizes the private storage if necessary and access to the long element at the given index
(public member function of std::ios_base) [edit]
resizes the private storage if necessary and access to the void* element at the given index
(public member function of std::ios_base) [edit]
Miscellaneous
registers event callback function
(public member function of std::ios_base) [edit]
sets whether C++ and C I/O libraries are interoperable
(public static member function of std::ios_base) [edit]
Member classes
stream exception
(public member class of std::ios_base) [edit]
initializes standard stream objects
(public member class of std::ios_base) [edit]

Member types and constants

Type Explanation
stream open mode type

The following constants are also defined:

Constant Explanation[edit]
app seek to the end of stream before each write[edit]
binary open in binary mode[edit]
in open for reading[edit]
out open for writing[edit]
trunc discard the contents of the stream when opening[edit]
ate seek to the end of stream immediately after open[edit]
noreplace (C++23) open in exclusive mode[edit]

(typedef) [edit]
formatting flags type

The following constants are also defined:

Constant Explanation[edit]
dec use decimal base for integer I/O: see std::dec[edit]
oct use octal base for integer I/O: see std::oct[edit]
hex use hexadecimal base for integer I/O: see std::hex[edit]
basefield dec | oct | hex. Useful for masking operations[edit]
left left adjustment (adds fill characters to the right): see std::left[edit]
right right adjustment (adds fill characters to the left): see std::right[edit]
internal internal adjustment (adds fill characters to the internal designated point): see std::internal[edit]
adjustfield left | right | internal. Useful for masking operations[edit]
scientific generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific[edit]
fixed generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed[edit]
floatfield scientific | fixed. Useful for masking operations[edit]
boolalpha insert and extract bool type in alphanumeric format: see std::boolalpha[edit]
showbase generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase[edit]
showpoint generate a decimal-point character unconditionally for floating-point number output: see std::showpoint[edit]
showpos generate a + character for non-negative numeric output: see std::showpos[edit]
skipws skip leading whitespace before certain input operations: see std::skipws[edit]
unitbuf flush the output after each output operation: see std::unitbuf[edit]
uppercase replace certain lowercase letters with their uppercase equivalents in certain output operations: see std::uppercase[edit]

(typedef) [edit]
state of the stream type

The following constants are also defined:


(typedef) [edit]
seeking direction type

The following constants are also defined:


(typedef) [edit]
specifies event type
(enum) [edit]
callback function type
(typedef) [edit]

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