Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

 
clog
 
 - Controls output to a stream buffer associated with the object stderr declared in <cstdio>.
 
 
 

SYNOPSIS

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

DESCRIPTION

 
 
The object clog controls output to a stream buffer associated with the object stderr declared in <cstdio>. The difference between clog and cerr is that clog is buffered but cerr is not. Therefore, commands like clog << "ERROR !!"; and fprintf(stderr,"ERROR !!"); are not synchronized. 
 
 
 

FORMATTING

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

EXAMPLE

 
 
 
//
// clog 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

clog << "Error while opening the file" << endl;

}
 
 
 

WARNINGS

 
 
clog can be used to redirect some of the errors to another recipient. For example, you might want to redirect them to a file named my_err:
 
 
ofstream out("my_err");
if ( out )

clog.rdbuf(out.rdbuf());

 
else
 

cerr << "Error while opening the file" << endl;
 
Then when you are doing something like clog << "error number x"; the error message is output to the file my_err. Obviously, you can use the same scheme to redirect clog to other devices. 
 
If your compiler does not support namespaces, then you do not need the using declaration for std. 
 
 
 

SEE ALSO

 
 
basic_ostream(3C++), basic_iostream(3C++), basic_filebuf(3C++), cout(3C++), cin(3C++), cerr(3C++), wcin(3C++), wcout(3C++), wcerr(3C++), wclog(3C++), iomanip(3C++), ios_base(3C++), basic_ios(3C++),
 
Working Paper for Draft Proposed International Standard for Information Systems--Programming Language C++, Section 27.3.1
 
 
 

STANDARDS CONFORMANCE

 
 
ANSI X3J16/ISO WG21 Joint C++ Committee
 

Rogue Wave Software  —  Last change: 02 Apr 1998