std::basic_istream::operator>>

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Input/output library

I/O manipulators

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

strstreambuf (deprecated)

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

istrstream (deprecated)

ostrstream (deprecated)

strstream (deprecated)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

std::basic_istream

Global objects

cinwcin

Member functions

basic_istream::basic_istream

basic_istream::~basic_istream

basic_istream::operator= (C++11)

Formatted input

basic_istream::operator>>

Unformatted input

basic_istream::get

basic_istream::peek

basic_istream::unget

basic_istream::putback

basic_istream::getline

basic_istream::ignore

basic_istream::read

basic_istream::readsome

basic_istream::gcount

Positioning

basic_istream::tellg

basic_istream::seekg

Miscellaneous

basic_istream::sync

basic_istream::swap (C++11)

Member classes

basic_istream::sentry

Non-member functions

operator>>(std::basic_istream)

 

basic_istream& operator>>( short& value ); basic_istream& operator>>( unsigned short& value );	(1)
basic_istream& operator>>( int& value ); basic_istream& operator>>( unsigned int& value );	(2)
basic_istream& operator>>( long& value ); basic_istream& operator>>( unsigned long& value );	(3)
basic_istream& operator>>( long long& value ); basic_istream& operator>>( unsigned long long& value );	(4)	(since C++11)
basic_istream& operator>>( float& value ); basic_istream& operator>>( double& value ); basic_istream& operator>>( long double& value );	(5)
basic_istream& operator>>( bool& value );	(6)
basic_istream& operator>>( void*& value );	(7)
basic_istream& operator>>( std::ios_base& (*func)(std::ios_base&) );	(8)
basic_istream& operator>>( std::basic_ios<CharT,Traits>& (*func)(std::basic_ios<CharT,Traits>&) );	(9)
basic_istream& operator>>( basic_istream& (*func)(basic_istream&) );	(10)
basic_istream& operator>>( std::basic_streambuf<CharT,Traits>* sb );	(11)

1-4) Behaves as a FormattedInputFunction. After constructing and checking the sentry object, which may skip leading whitespace, extracts an integer value by calling std::num_get::get()

5) Behaves as a FormattedInputFunction. After constructing and checking the sentry object, which may skip leading whitespace, extracts a floating point value by calling std::num_get::get()

6) Behaves as a FormattedInputFunction. After constructing and checking the sentry object, which may skip leading whitespace, extracts bool value by calling std::num_get::get()

7) Behaves as a FormattedInputFunction. After constructing and checking the sentry object, which may skip leading whitespace, extracts a generic pointer value by calling std::num_get::get()

8-10) Calls func(*this);, where func is an I/O manipulator.

11) Behaves as an UnformattedInputFunction. After constructing and checking the sentry object, extracts all data from the input stream and stores it to sb. The extraction stops if one of the following conditions are met:

• end-of-file occurs on the input sequence;
• inserting in the output sequence fails (in which case the character to be inserted is not extracted);
• an exception occurs (in which case the exception is caught, and only rethrown if failbit is enabled in exceptions()).

In either case, stores the number of characters extracted in the member variable accessed by subsequent calls to gcount(). If sb is a null pointer of it no characters were inserted into sb, calls setstate(failbit) (which may throw std::ios_base::failure if enabled).

If extraction fails (e.g. if a letter was entered where a digit is expected), value is left unmodified and failbit is set.	(until C++11)
If extraction fails, zero is written to value and failbit is set. If extraction results in the value too large or too small to fit in value, std::numeric_limits<T>::max() or std::numeric_limits<T>::min() is written and failbit flag is set.	(since C++11)

Parameters

value	-	reference to an integer or floating-point value to store the extracted value to
func	-	pointer to I/O manipulator function
sb	-	pointer to the streambuffer to write all the data to

Return value

1-9,11) *this

10) func(*this)

Example

Run this code

#include <iostream>
#include <iomanip>
#include <sstream>
 
int main()
{
    std::string input = "41 3.14 false hello world";
    std::istringstream stream(input);
    int n;
    double f;
    bool b;
 
    stream >> n >> f >> std::boolalpha >> b;
    std::cout << "n = " << n << '\n'
              << "f = " << f << '\n'
              << "b = " << std::boolalpha << b << '\n';
 
    // extract the rest using the streambuf overload
    stream >> std::cout.rdbuf();
    std::cout << '\n';
}

Output:

n = 41
f = 3.14
b = false
hello world

See also

operator>>(std::basic_istream)	extracts characters and character arrays (function template)
operator<<operator>>	performs stream input and output on strings (function template)
operator<<operator>>	performs stream input and output of bitsets (function template)
operator<<operator>>	serializes and deserializes a complex number (function template)
operator<<operator>>	performs stream input and output on pseudo-random number engine (function template)
operator<<operator>>	performs stream input and output on pseudo-random number distribution (function template)
read	extracts blocks of characters (public member function)
readsome	extracts already available blocks of characters (public member function)
get	extracts characters (public member function)
getline	extracts characters until the given character is found (public member function)