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The object cerr controls output to a stream buffer associated with the object stderr, declared in <cstdio>.

extern ostream cerr;

The object controls unbuffered insertions to the standard error output as a byte stream. Once the object is constructed, the expression cerr.flags & unitbuf is nonzero, and cerr.tie() == &cout.

// iostream_cerr.cpp
// compile with: /EHsc
#include <iostream>
#include <fstream>

using namespace std;

void TestWide( ) 
   int i = 0;
   wcout << L"Enter a number: ";
   wcin >> i;
   wcerr << L"test for wcerr" << endl;
   wclog << L"test for wclog" << endl;   

int main( ) 
   int i = 0;
   cout << "Enter a number: ";
   cin >> i;
   cerr << "test for cerr" << endl;
   clog << "test for clog" << endl;
   TestWide( );

Enter a number: 3
test for cerr
test for clog
Enter a number: 1
test for wcerr
test for wclog

Header: <iostream>

Namespace: std

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