std::clog, std::wclog

< cpp‎ | io
Defined in header <iostream>
extern std::ostream clog;
extern std::wostream wclog;

The global objects std::clog and std::wclog control output to a stream buffer of implementation-defined type (derived from std::streambuf), associated with the standard C output stream stderr, but, unlike std::cerr/std::wcerr, these streams are not automatically flushed and cout is not automatically tie()'d with these streams.

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.

[edit] Notes

The 'c' in the name refers to "character" ( FAQ); clog means "character log" and wclog means "wide character log".

[edit] Example

#include <iostream>
struct Foo
    int n;
        std::clog << "static constructor\n";
        std::clog << "static destructor\n";
Foo f; // static object
int main()
    std::clog << "main function\n";


static constructor
main function
static destructor

[edit] See also

initializes standard stream objects
(public member class of std::ios_base) [edit]
writes to the standard C error stream stderr, unbuffered
(global object)[edit]
writes to the standard C output stream stdout
(global object)[edit]
expression of type FILE* associated with the input stream
expression of type FILE* associated with the output stream
expression of type FILE* associated with the error output stream
(macro constant) [edit]