AixLog

Header-only C++ logging library

Features

• Single header file implementation
  • Simply include and use it!
  • No dependcies, just vanilla C++11
• Permissive MIT license
• Use ostream operator <<
  • Unobtrusive, typesafe and expressive
  • Easy to switch from existing “cout logging”
• Fancy name
• Native support for various platforms (through Sinks)
  • Linux, Unix: Syslog
  • macOS: Unified logging (os_log), Syslog (<10.12)
  • Android: Android Log
  • Windows: Event log, OutputDebugString
• Several Sinks:
  • cout
  • cerr
  • Sink with custom callback function
    • implement your own log sink in a lambda with a single line of code
  • Easy to add more…
• Manipulators for
  • Different log levels: TRACE, DEBUG, INFO, NOTICE, WARNING, ERROR, FATAL
LOG(ERROR) << "some error happened!"
LOG(DEBUG) << "Just a debug message"
  • Conditional logging: simply put COND(bool) in front
    LOG(INFO) << COND(false) << "will not be logged\n"
LOG(INFO) << COND(true) << "will be logged\n"
  • Support for tags:
    LOG(INFO, "my tag") << "some message"
    …is the same as…
    LOG(INFO) << TAG("my tag") << "some message"
  • Capture function and line number and timestamp
  • Filters: filter by tag and/or by severity what message is logged where, e.g.
    • Add a syslog sink with the filters *:error, SYSLOG:trace to receive only messages with severity error or with tag SYSLOG
    • Add another cout sink with filter *:debug to receive all messages with debug or higher severity
  • Support for colors:
    • Foreground: LOG(INFO) << COLOR(red) << "red foreground"
    • Foreground and background: LOG(INFO) << COLOR(yellow, blue) << "yellow on blue background"

Basic usage

To use AixLog, you must once pass a log sink to AixLog:init, e.g. a SinkCout:

AixLog::Log::init<AixLog::SinkCout>(AixLog::Severity::trace);
LOG(INFO) << "Hello, World!\n";

This will print

2017-09-28 11-01-16.049 [Info] (main) Hello, World!

There are two overloads for AixLog:init:

1. one creates and returns an instance of a Sink (as in the example above)

   auto sink = AixLog::init<AixLog::SinkCout>(AixLog::trace);

The sink can be used to change the severity or to remove it from the Logger

1. one takes a vector of Sinks

   auto sink_cout = make_shared<AixLog::SinkCout>(AixLog::trace);
   auto sink_file = make_shared<AixLog::SinkFile>(AixLog::trace, "logfile.log");
   AixLog::init({sink_cout, sink_file});

This will log to both: cout and to file logfile.log

Advanced usage

You can easily fit AixLog to your needs by adding your own sink, that derives from the Sink class. Or even more simple, by using SinkCallback with a custom call back function:

AixLog::Log::init<AixLog::SinkCallback>(AixLog::Severity::trace, AixLog::Type::all, 
    [](const AixLog::Metadata& metadata, const std::string& message)
    {
        cout << "Callback:\n\tmsg:   " << message << "\n\ttag:   " << metadata.tag.text << "\n\tsever: " << AixLog::Log::to_string(metadata.severity) << " (" << (int)metadata.severity << "\n";
        if (metadata.timestamp)
            cout << "\ttime:  " << metadata.timestamp.to_string() << "\n";
        if (metadata.function)
            cout << "\tfunc:  " << metadata.function.name << "\n\tline:  " << metadata.function.line << "\n\tfile:  " << metadata.function.file << "\n";
    }
);
LOG(INFO) << TAG("test") << "Hello, Lambda!\n";

This will print

Callback:
    msg:   Hello, Lambda!
    tag:   test
    sever: Info (2)
    type:  normal
    time:  2017-09-28 11-46-32.179
    func:  main
    line:  36
    file:  aixlog_test.cpp

Usage example

#include "aixlog.hpp"
using namespace std;
int main(int argc, char** argv)
{
    AixLog::Log::init(
        {
            /// Log normal (i.e. non-special) logs to SinkCout
            make_shared<AixLog::SinkCout>(AixLog::Severity::trace, "cout: %Y-%m-%d %H-%M-%S.#ms [#severity] (#tag) #message"),
            /// Log error and higher severity messages to cerr
            make_shared<AixLog::SinkCerr>(AixLog::Severity::error, AixLog::Type::all, "cerr: %Y-%m-%d %H-%M-%S.#ms [#severity] (#tag)"),
            /// Log special logs to native log (Syslog on Linux, Android Log on Android, EventLog on Windows, Unified logging on Apple)
            make_shared<AixLog::SinkNative>("aixlog", AixLog::Severity::trace, AixLog::Type::special),
            /// Callback log sink with cout logging in a lambda function
            /// Could also do file logging
            make_shared<AixLog::SinkCallback>(AixLog::Severity::trace, AixLog::Type::all, 
                [](const AixLog::Metadata& metadata, const std::string& message)
                {
                    cout << "Callback:\n\tmsg:   " << message << "\n\ttag:   " << metadata.tag.text << "\n\tsever: " << AixLog::Log::to_string(metadata.severity) << " (" << (int)metadata.severity << "\n";
                    if (metadata.timestamp)
                        cout << "\ttime:  " << metadata.timestamp.to_string() << "\n";
                    if (metadata.function)
                        cout << "\tfunc:  " << metadata.function.name << "\n\tline:  " << metadata.function.line << "\n\tfile:  " << metadata.function.file << "\n";
                }
            )
        }
    );
    /// Log with info severity
    LOG(INFO) << "LOG(INFO)\n";
    /// ... with a tag
    LOG(INFO, "guten tag") << "LOG(INFO, \"guten tag\")\n";
    /// ... with an explicit tag (same result as above)
    LOG(INFO) << TAG("guten tag") << "LOG(INFO) << TAG(\"guten tag\")\n";
    /// Different log severities
    LOG(FATAL) << "LOG(FATAL)\nLOG(FATAL) Second line\n";
    LOG(FATAL) << TAG("hello") << "LOG(FATAL) << TAG(\"hello\") no line break";
    LOG(FATAL) << "LOG(FATAL) 2 no line break";
    LOG(ERROR) << "LOG(ERROR): change in log-level will add a line break";
    LOG(WARNING) << "LOG(WARNING)";
    LOG(NOTICE) << "LOG(NOTICE)";
    LOG(INFO) << "LOG(INFO)\n";
    LOG(INFO) << TAG("my tag") << "LOG(INFO) << TAG(\"my tag\")n";
    LOG(DEBUG) << "LOG(DEBUG)\n";
    LOG(TRACE) << "LOG(TRACE)\n";
    /// Conditional logging
    LOG(DEBUG) << COND(1 == 1) << "LOG(DEBUG) will be logged\n";
    LOG(DEBUG) << COND(1 == 2) << "LOG(DEBUG) will not be logged\n";
    /// Colors :-)
    LOG(FATAL) << "LOG(FATAL) " << AixLog::Color::red << "red" << AixLog::Color::none << ", default color\n";
    LOG(FATAL) << "LOG(FATAL) " << COLOR(red) << "red" << COLOR(none) << ", default color (using macros)\n";
    LOG(FATAL) << "LOG(FATAL) " << AixLog::TextColor(AixLog::Color::yellow, AixLog::Color::blue) << "yellow on blue background" << AixLog::Color::none << ", default color\n";
    LOG(FATAL) << "LOG(FATAL) " << COLOR(yellow, blue) << "yellow on blue background" << COLOR(none) << ", default color (using macros)\n";
}