cerr

Pre-defined stream

• Summary
• Data Type and Member Function Indexes
• Synopsis
• Description
• Formatting
• Example
• See Also
• Standards Conformance

Controls output to an unbuffered stream buffer associated with the object stderr declared in <cstdio>.

None

#include <iostream>
extern ostream cerr;
ostream cerr;

The object cerr controls output to an unbuffered stream buffer associated with the object stderr declared in <cstdio>. By default, the standard C and C++ streams are synchronized, but you can improve performance by using the ios_base member function synch_with_stdio to desynchronize them.

The formatting is done through member functions or manipulators. See cout or basic_ostream for details.

//
// cerr example
//
#include<iostream>
#include<fstream>

void main ( )
{
  using namespace std;

  // open the file "file_name.txt"
  // for reading
  ifstream in("file_name.txt");
 
  // output the all file to stdout
  if ( in ) 
    cout << in.rdbuf(); 
  else
    // if the ifstream object is in a bad state
    // output an error message to stderr
    cerr << "Error while opening the file" << endl; 
}

basic_ostream(3C++), iostream(3C++), basic_filebuf(3C++), cout(3C++), cin(3C++), clog(3C++), wcin(3C++), wcout(3C++), wcerr(3C++), iomanip(3C++), wclog(3C++), ios_base(3C++), basic_ios(3C++)

Working Paper for Draft Proposed International Standard for Information Systems--Programming Language C++, Section 27.3.1

ANSI X3J16/ISO WG21 Joint C++ Committee