std::basic_istream

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

The class template basic_istream provides support for high level input operations on character streams. The supported operations include formatted input (e.g. integer values or whitespace-separated characters and characters strings) and unformatted input (e.g. raw characters and character arrays). This functionality is implemented in terms of the interface provided by the underlying basic_streambuf class, accessed through the basic_ios base class. The only non-inherited data member of basic_istream, in most implementations, is the value returned by basic_istream::gcount().

Inheritance diagram

Two specializations for common character types are defined:

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Global objects

Two global basic_istream objects are provided by the standard library.

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Defined in header <iostream>

Member types

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Member functions

Template:cpp/io/basic istream/dcl list constructorTemplate:cpp/io/basic istream/dcl list destructorTemplate:cpp/io/basic istream/dcl list operator=Template:cpp/io/basic istream/dcl list operator gtgtTemplate:cpp/io/basic istream/dcl list getTemplate:cpp/io/basic istream/dcl list peekTemplate:cpp/io/basic istream/dcl list ungetTemplate:cpp/io/basic istream/dcl list putbackTemplate:cpp/io/basic istream/dcl list getlineTemplate:cpp/io/basic istream/dcl list ignoreTemplate:cpp/io/basic istream/dcl list readTemplate:cpp/io/basic istream/dcl list readsomeTemplate:cpp/io/basic istream/dcl list gcountTemplate:cpp/io/basic istream/dcl list tellgTemplate:cpp/io/basic istream/dcl list seekgTemplate:cpp/io/basic istream/dcl list syncTemplate:cpp/io/basic istream/dcl list swap

Formatted input

Unformatted input

Positioning

Miscellaneous

Member classes

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Non-member functions

Template:cpp/io/basic istream/dcl list operator gtgt2

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)