Small logger class

Question

I am looking for a small lightweight logging system in c++. I have found some existing frameworks but I don\'t need all of their features at this point in time. I primarily

Answer 1

I strongly recommend this simple logging system: http://www.drdobbs.com/cpp/201804215. It is composed of a single header file. I have successfully used it on Linux, Windows and Mac OS X.

You write to the log like this:

FILE_LOG(logWARNING) << "Ops, variable x should be " << expectedX << "; is " << realX;

I really like the stream syntax. It is unobtrusive, typesafe and expressive. The logging framework automatically adds a \n at the end of the line, plus date, time and indentation.

Configuring the logs is pretty easy:

FILELog::ReportingLevel() = logDEBUG3;
FILE* log_fd = fopen( "mylogfile.txt", "w" );
Output2FILE::Stream() = log_fd;

This framework is also easy to extend. At work, we have recently made some adaptations to it so that it now uses an std::ofstream instead of a FILE*. As a result, we are now able to add nice features such as encrypting the logs, by chaining the streams.

Answer 2

If you don't have size limitations on the project and you expect it to live a long time, I would suggest looking at Apache Log4cxx. It's not a small library, but it supports just about everything you ever wanted (including some things you didn't even knew you wanted) in logging, and it's portable.

In any larger project sooner or later you'll want your logging solution to do more than a "small logger class", so indeed why reinvent the wheel.

Answer 3

I, as well as many others, also answered this question with some code.

This isn't really "ready" in all ways, but it could be easily modified:

https://gist.github.com/earonesty/977b14c93358fe9b9ee674baac5d42d7

Features:

• writing to the log doesn't block on i/o
• similar macros to other solutions (LOGE(blah << stream))
• prefers discarding log entries to slowing down
• lazy flushing
• header only, very small, stl classes only
• tested on osx/win/nix
• time format is configurable

Missing stuff:

• easy, flexible log formatting (predefining a macro would be fine)
• triggers have an interface but don't work yet
• microseconds aren't working yet

If anyone actually likes this solution in any way, lmk and I'll make a real repo out of it with tests, etc. It's pretty fast. Probably not as fast as speedlogger (a heavier feature complete library), but not sure.