# operator>>(std::basic_istream)

From cppreference.com
< cpp‎ | io‎ | 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) |
| (2) |
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 ); |  | (until C++20)

template< class CharT, class Traits, std::size_t N >

basic_istream<CharT,Traits>& operator>>( basic_istream<CharT,Traits>& st, CharT (&s)[N] );
template< class Traits, std::size_t N >
basic_istream<char,Traits>& operator>>( basic_istream<char,Traits>& st, signed char (&s)[N] );
template< class Traits, std::size_t N >

basic_istream<char,Traits>& operator>>( basic_istream<char,Traits>& st, unsigned char (&s)[N] );

(since C++20)

| (3) |
template< class CharT, class Traits, class T > basic_istream<CharT,Traits>& operator>>( basic_istream<CharT,Traits>&& st, T& value ); |  | (since C++11) (until C++17)
template< class CharT, class Traits, class T > basic_istream<CharT,Traits>& operator>>( basic_istream<CharT,Traits>&& st, T&& value ); |  | (since C++17)

1-2) 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 (until C++20) `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 (if st.width() is greater than zero)

(until C++20)

  - min(std::size_t(st.width()), N) - 1 characters are extracted (if st.width() is greater than zero)
  - N - 1 characters are extracted otherwise

(since C++20)

  - 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). | (since C++11) (until C++17)
Calls the appropriate extraction operator, given an rvalue reference to an input stream object (equivalent to st >> std::forward<T>(value)). This function does not participate in overload resolution unless the expression st >> std::forward<T>(value) is well-formed. | (since C++17)

### 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 (until C++20) a character array 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)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/io/basic_istream/operator_gtgt2&oldid=106958"