LogForCpp (log4cpp) http://log4cpp.sourceforge.net/
Log4cpp is library of C++ classes for flexible logging to files, syslog, IDSA and other destinations. It is modeled after the Log4j Java library, staying as close to their API as is reasonable.
Installation
Release Name: log4cpp-0.3.5rc3 2005-07-29
I have had a slight problem installing this on Linux Fedora Core 4 with GnuCpp 4.0.2. The problem is an extra semicolon at the end of the namespace log4cpp declared in include/log4cpp/Manipulator.hh. After that it builds and all except one of the checks run O.K. There is not a simple example in the documentation but there is an article which describes how to use log4cpp at http://developers.sun.com/solaris/articles/logging.html which includes some example code.
-- JohnFletcher
See also PatternsForLoggingDiagnosticMessages, LogForJava, LogForRuby