clog (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.
NAME
clog
SYNOPSIS
#include <iostream>
extern ostream clog;
DESCRIPTION
ostream clog;
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.
EXAMPLES
//
// 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.
SEE ALSO
basic_ostream(3C++std), iostream(3C++std), basic_filebuf(3C++std),
cout(3C++std), cin(3C++std), cerr(3C++std), wcin(3C++std), wcout(3C++std),
wcerr(3C++std), wclog(3C++std), iomanip(3C++std), ios_base(3C++std),
basic_ios(3C++std),
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
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