std::cin, std::wcin

Template:cpp/io/basic istream/sidebar Template:ddcl list begin <tr class="t-dsc-header">

<td>

Defined in header <iostream>

</td>

<td></td> <td></td> </tr> <tr class="t-dcl ">

<td >

extern std::istream cin;

</td>

<td > (1) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl ">

<td >

extern std::wistream wcin;

</td>

<td > (2) </td> <td class="t-dcl-nopad"> </td> </tr> Template:ddcl list end

The global objects Template:cpp and Template:cpp control input from a stream buffer of implementation-defined type (derived from Template:cpp), associated with the standard C input stream Template:cpp.

These objects are guaranteed to be constructed before the first constructor of a static object is called and they are guaranteed to outlive the last destructor of a static object, so that it is always possible to read from Template:cpp in user code.

Unless Template:cpp has been issued, it is safe to concurrently access these objects from multiple threads for both formatted and unformatted input.

Once Template:cpp is constructed, Template:cpp returns Template:cpp, and likewise, Template:cpp returns Template:cpp. This means that any formatted input operation on Template:cpp forces a call to Template:cpp if any characters are pending for output.

Example

Run this code

#include <iostream>
struct Foo {
    int n;
    Foo() {
       std::cout << "Enter n: "; // no flush needed
       std::cin >> n;
    }
};
Foo f; // static object
int main()
{
    std::cout << "f.n is " << f.n << '\n';
}

Output:

Enter n: 10
f.n is 10

See also

Template:cpp/io/ios base/dcl list InitTemplate:cpp/io/dcl list cout