NAME¶

std::cout,std::wcout - std::cout,std::wcout

Synopsis¶

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 with ordered initialization (as long
as <iostream> is included before the object is defined).

Unless std::ios_base::sync_with_stdio(false) has been issued, it is safe to
concurrently access these objects from multiple threads for both formatted and
unformatted output.

By specification of std::cin, std::cin.tie() returns &std::cout. This means that any
input operation on std::cin executes std::cout.flush() (via
std::basic_istream::sentry's constructor). Similarly, std::wcin.tie() returns
&std::wcout.

By specification of std::cerr, std::cerr.tie() returns &std::cout. This means that
any output operation on std::cerr executes std::cout.flush() (via
std::basic_ostream::sentry's constructor). Similarly, std::wcerr.tie() returns
&std::wcout. (since C++11)

Notes¶

The 'c' in the name refers to "character" (stroustrup.com FAQ); cout means
"character output" and wcout means "wide character output".

Because dynamic initialization of templated variables are unordered, it is not
guaranteed that std::cout has been initialized to a usable state before the
initialization of such variables begins, unless an object of type
std::ios_base::Init has been constructed.

Example¶

// Run this code

#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

See also¶

Init initializes standard stream objects
(public member class of std::ios_base)
cerr writes to the standard C error stream stderr, unbuffered
wcerr (global object)
clog writes to the standard C error stream stderr
wclog (global object)
stdin expression of type FILE* associated with the input stream
stdout expression of type FILE* associated with the output stream
stderr expression of type FILE* associated with the error output stream
(macro constant)