operator>>(std::basic_istream)

 

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)

 

template< class CharT, class Traits > basic_istream<CharT,Traits>& operator>>( basic_istream<CharT,Traits>& st, CharT& ch ); template< class Traits > basic_istream<char,Traits>& operator>>( basic_istream<char,Traits>& st, signed char& ch ); template< class Traits > basic_istream<char,Traits>& operator>>( basic_istream<char,Traits>& st, unsigned char& ch );	(1)
template< class CharT, class Traits> basic_istream<CharT,Traits>& operator>>( basic_istream<CharT,Traits>& st, CharT* s ); template< class Traits > basic_istream<char,Traits>& operator>>( basic_istream<char,Traits>& st, signed char* s ); template< class Traits > basic_istream<char,Traits>& operator>>( basic_istream<char,Traits>& st, unsigned char* s );	(2)
template< class CharT, class Traits, class T > basic_istream<CharT,Traits>& operator>>( basic_istream<CharT,Traits>&& st, T& value );	(3)	(since C++11)

Performs character input operations.

1) Behaves as an FormattedInputFunction. After constructing and checking the sentry object, which may skip leading whitespace, extracts a character and stores it to ch. If no character is available, sets failbit (in addition to eofbit that is set as required of a FormattedInputFunction).

2) Behaves as an FormattedInputFunction. After constructing and checking the sentry object, which may skip leading whitespace, extracts successive characters and stores them at successive locations of a character array whose first element is pointed to by s. The extraction stops if one of the following conditions are met:

• a whitespace character (as determined by the ctype<CharT> facet) is found. The whitespace character is not extracted.
• st.width() - 1 characters are extracted
• end of file occurs in the input sequence (this also sets eofbit)

In either case, an additional null character value CharT() is stored at the end of the output. If no characters were extracted, sets failbit (the null character is still written, to the first position in the output). Finally, calls st.width(0) to cancel the effects of std::setw, if any.

3) Calls the appropriate extraction operator, given an rvalue reference to an input stream object (equivalent to st >> value).

Notes

Extracting a single character that is the last character of the stream does not set eofbit: this is different from other formatted input functions, such as extracting the last integer with operator>>, but this behavior matches the behavior of std::scanf with "%c" format specifier.

Parameters

st	-	input stream to extract the data from
ch	-	reference to a character to store the extracted character to
s	-	pointer to a character string to store the extracted characters to

Return value

st

Example

Run this code

#include <iostream>
#include <iomanip>
#include <sstream>
 
int main()
{
    std::string input = "n greetings";
    std::istringstream stream(input);
    char c;
    const int MAX = 6;
    char cstr[MAX];
 
    stream >> c >> std::setw(MAX) >> cstr;
    std::cout << "c = " << c << '\n'
              << "cstr = " << cstr << '\n';
 
    double f;
    std::istringstream("1.23") >> f; // rvalue stream extraction
    std::cout << "f = " << f << '\n';
}

Output:

c = n
cstr = greet
f = 1.23

See also

operator>>

extracts formatted data (public member function)