The global objectsstd::cout andstd::wcout control output to a stream buffer of implementation-defined type (derived fromstd::streambuf), associated with the standard C output streamstdout.

These objects are guaranteed to be initialized during or before the first time an object of typestd::ios_base::Init is constructed and are available for use in the constructors and destructors of static objects withordered initialization (as long as<iostream> is included before the object is defined).

Unlessstd::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 ofstd::cin,std::cin.tie() returns&std::cout. This means that any input operation onstd::cin executesstd::cout.flush() (viastd::basic_istream::sentry's constructor). Similarly,std::wcin.tie() returns&std::wcout.

By specification ofstd::cerr,std::cerr.tie() returns&std::cout. This means that any output operation onstd::cerr executesstd::cout.flush() (viastd::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" andwcout means "wide character output".

Becausedynamic initialization oftemplated variables are unordered, it is not guaranteed thatstd::cout has been initialized to a usable state before the initialization of such variables begins, unless an object of typestd::ios_base::Init has been constructed.

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";}

static constructormain functionstatic destructor

See also

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