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std::clog, std::wclog

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Revision as of 05:50, 27 March 2013 by SuperBoi45 (Talk | contribs)

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<td>
Defined in header <iostream>
</td>

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<td >
extern std::ostream clog;
</td>

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extern std::wostream wclog;
</td>

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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 constructed before the first constructor of a static object is called and they are guaranteed to outlive the last destructor of a static object, so that it is always possible to write to std::clog in user code.

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.

Example

#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

Template:cpp/io/ios base/dcl list InitTemplate:cpp/io/dcl list cerrTemplate:cpp/io/dcl list cout