std::basic_istream::operator>> - cppreference.com

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# std::basic_istream::operator>>

From cppreference.com
< cpp‎ | io‎ | 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>>( basic_istream& st, std::ios_base& (*func)(std::ios_base&) ); basic_istream& operator>>( basic_istream& st, std::basic_ios<CharT,Traits>& (*func)(std::basic_ios<CharT,Traits>&) ); basic_istream& operator>>( basic_istream& st, std::basic_istream& (*func)(std::basic_istream&) ); | (8) |
basic_istream& operator>>( basic_istream& st, std::basic_streambuf<CharT,Traits>* sb ); | (9) |

1-4) Behaves as an `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 an `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 an `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 an `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) Calls func(*this);, where `func` is an I/O manipulator.

9) 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 exceptions on `failbit` are enabled).

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 or if no characters are inserted into `sb`, sets `eofbit`.

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)

### [edit] 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

### [edit] Return value

*this

### [edit] 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

### [edit] See also

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

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