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

For anyone wanting a simple solution, I recommend: easylogging++

Single header only C++ logging library. It is extremely light-weight, robust, fast performing, thread and type safe and consists of many built-in features. It provides ability to write logs in your own customized format. It also provide support for logging your classes, third-party libraries, STL and third-party containers etc.

This library has everything built-in to prevent usage of external libraries.

Simple example: (more advanced examples available on the link above).

#include "easylogging++.h"

INITIALIZE_EASYLOGGINGPP

int main(int argv, char* argc[]) {
   LOG(INFO) << "My first info log using default logger";
   return 0;
}

Example output inside a class:

2015-08-28 10:38:45,900 DEBUG [default] [user@localhost] [Config::Config(const string)] [src/Config.cpp:7] Reading config file: 'config.json'

I tried log4cpp and boost::log but they are not as easy as this one.

EXTRA CONTENT: Minimal version - LOG header

I created a small code for even simpler applications based on easylogging but requires no initialization (be aware that it is probably not thread safe). Here is the code:

/* 
 * File:   Log.h
 * Author: Alberto Lepe 
 *
 * Created on December 1, 2015, 6:00 PM
 */

#ifndef LOG_H
#define LOG_H

#include 

using namespace std;

enum typelog {
    DEBUG,
    INFO,
    WARN,
    ERROR
};

struct structlog {
    bool headers = false;
    typelog level = WARN;
};

extern structlog LOGCFG;

class LOG {
public:
    LOG() {}
    LOG(typelog type) {
        msglevel = type;
        if(LOGCFG.headers) {
            operator << ("["+getLabel(type)+"]");
        }
    }
    ~LOG() {
        if(opened) {
            cout << endl;
        }
        opened = false;
    }
    template
    LOG &operator<<(const T &msg) {
        if(msglevel >= LOGCFG.level) {
            cout << msg;
            opened = true;
        }
        return *this;
    }
private:
    bool opened = false;
    typelog msglevel = DEBUG;
    inline string getLabel(typelog type) {
        string label;
        switch(type) {
            case DEBUG: label = "DEBUG"; break;
            case INFO:  label = "INFO "; break;
            case WARN:  label = "WARN "; break;
            case ERROR: label = "ERROR"; break;
        }
        return label;
    }
};

#endif  /* LOG_H */

Usage:

#include "Log.h"

int main(int argc, char** argv) {
    //Config: -----(optional)----
    structlog LOGCFG = {};
    LOGCFG.headers = false; 
    LOGCFG.level = DEBUG;
    //---------------------------
    LOG(INFO) << "Main executed with " << (argc - 1) << " arguments";
}

This code print the message using "cout", but you can change it to use "cerr" or append a file, etc. I hope its useful to someone. (Note: I'm not C++ expert in any way, so this code may explode in extreme cases).