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clog
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clog
Pre-defined stream
- Data Type and Member Function Indexes
- Synopsis
- Description
- Formatting
- Examples
- Warnings
- See Also
- Standards Conformance
Data Type and Member Function Indexes
(exclusive of constructors and destructors)
None
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++), 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
©Copyright 1996, Rogue Wave Software, Inc.