std::cout, std::wcout
| Defined in header <iostream>
|
||
| extern std::ostream cout; |
(1) | |
| extern std::wostream wcout; |
(2) | |
The global objects std::cout and std::wcout control output to a stream buffer of implementation-defined type (derived from std::streambuf), associated with the standard C output stream stdout.
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 (as long as <iostream> is included).
Unless sync_with_stdio(false) has been issued, it is safe to concurrently access these objects from multiple threads for both formatted and unformatted output.
Once initialized, std::cout is tie()'d to std::cin and std::wcout is tie()'d to std::wcin, meaning that any input operation on std::cin executes std::cout.flush() (via std::basic_istream::sentry's constructor).
Once initialized, std::cout is also tie()'d to std::cerr and std::wcout is tie()'d to std::wcerr, meaning that any output operation on std::cerr executes std::cout.flush() (via std::basic_ostream::sentry's constructor) (since C++11)
[edit] Example
#include <iostream> struct Foo { int n; Foo() { std::cout << "static constructor\n"; } ~Foo() { std::cout << "static destructor\n"; } }; Foo f; // static object int main() { std::cout << "main function\n"; }
Output:
static constructor main function static destructor
[edit] See also
| initializes standard stream objects (public member class of std::ios_base)
| |
| writes to the standard C error stream stderr, unbuffered (global object) | |
| writes to the standard C error stream stderr (global object) |
