# std::clog, std::wclog

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< cpp‎ | io

Defined in header `<iostream>` |  |
extern std::ostream clog; | (1) |
extern std::wostream wclog; | (2) |

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 not automatically tie()'d with cout.

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 output.

### Notes

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

### Example

Run this code

    #include <iostream>

    struct Foo {
        int n;
        Foo() {
           std::clog << "static constructor\n";
        }
        ~Foo() {
           std::clog << "static destructor\n";
        }
    };

    Foo f; // static object

    int main()
    {
        std::clog << "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 wcerr | writes to the standard C error stream stderr, unbuffered (global object)
cout wcout | writes to the standard C output stream stdout (global object)

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