The global objects std::cin and std::wcin control input from a stream buffer of implementation-defined type (derived from std::streambuf), associated with the standard C input stream stdin.
These objects are guaranteed to be initialized during or before the first time an object of type std::ios_base::Init is constructed and are available for use in the constructors and destructors of static objects with ordered initialization (as long as <iostream> is included before the object is defined).
Unless sync_with_stdio(false) has been issued, it is safe to concurrently access these objects from multiple threads for both formatted and unformatted input.
Once initialized:
1) std::cin.tie()returns
&std::cout. This means that any input operation on
std::cin
forces a call to
std::cout.flush()if any characters are pending for output..
2) std::wcin.tie()returns
&std::wcout. This means that any input operation on
std::wcin
forces a call to
std::wcout.flush()if any characters are pending for output.
[edit] NotesThe âcâ in the name refers to âcharacterâ (stroustrup.com FAQ); cin means âcharacter inputâ and wcin means âwide character inputâ.
#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';
}
Possible output:
[edit] See also initializes standard stream objectsstd::ios_base) [edit] writes to the standard C output stream stdout
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