std::istream::operator>>

(1) arithmetic types

Extracts and parses characters sequentially from the stream to interpret them as the representation of a value of the proper type, which is stored as the value of val.
Internally, the function accesses the input sequence by first constructing a sentry object (with noskipws set to false). Then (if good), it calls num_get::get (using the stream's selected locale) to perform both the extraction and the parsing operations, adjusting the stream's internal state flags accordingly. Finally, it destroys the sentry object before returning.

(2) stream buffers

Extracts as many characters as possible from the stream and inserts them into the output sequence controlled by the stream buffer object pointed by sb (if any), until either the input sequence is exhausted or the function fails to insert into the object pointed by sb.

The function is considered to perform formatted input: Internally, the function accesses the input sequence by first constructing a sentry object (with noskipws set to false). Then (if good), it extracts characters from its associated stream buffer object as if calling its member functions sbumpc or sgetc, and finally destroys the sentry object before returning.

The function is considered to perform unformatted input: Internally, the function accesses the input sequence by first constructing a sentry object (with noskipws set to true). Then (if good), it extracts characters from its associated stream buffer object as if calling its member functions sbumpc or sgetc, and finally destroys the sentry object before returning.
The number of characters successfully read and stored by this function can be accessed by calling member gcount.

(3) manipulators

Calls pf(*this), where pf may be a manipulator.
Manipulators are functions specifically designed to be called when used with this operator.
This operation has no effect on the input sequence and extracts no characters (unless the manipulator itself does, like ws).

Parameters

val

Object where the value that the extracted characters represent is stored.
Notice that the type of this argument (along with the stream's format flags) influences what constitutes a valid representation.

sb

Pointer to a streambuf object on whose controlled output sequence the characters are copied.

pf

A function that takes and returns a stream object. It generally is a manipulator function.
The standard manipulators which have an effect when used on standard istream objects are:

manipulator	Effect
ws	Extracts whitespaces.
boolalpha/noboolalpha	Activates/deactivates the extraction of alphanumerical representations of values of type bool.
skipws/noskipws	Activates/deactivates whether leading whitespaces are discarded before formatted input operations.
dec/hex/oct	Sets that base used to interpret integral numerical values.

The following extended manipulators can also be applied to istream objects (these take additional arguments and require the explicit inclusion of the <iomanip> header):

manipulator	Effect
setbase	Sets the numerical base used to interpret integral numerical values.
setiosflags/resetiosflags	Set/reset format flags.

Return Value

Example

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// example on extraction
#include <iostream>     // std::cin, std::cout, std::hex
int main () {
  int n;
  std::cout << "Enter a number: ";
  std::cin >> n;
  std::cout << "You have entered: " << n << '\n';
  std::cout << "Enter a hexadecimal number: ";
  std::cin >> std::hex >> n;         // manipulator
  std::cout << "Its decimal equivalent is: " << n << '\n';
  return 0;
}

Data races

Exception safety

See also

istream::get

Get characters (public member function)

istream::getline

Get line (public member function)

ostream::operator<<

Insert formatted output (public member function)

istream::sentry

Prepare stream for input (public member class)