Logger

A simple C++ logging setup that builds on spdlog to provide easily configurable console and file outputs, along with convenient logging macros.

Features

• Console and File output sinks.
• Configurable log levels, file sizes, and rotation behavior.
• Log macros (LOG_INFO, LOG_ERROR, etc.) with fmt formatting.
• Simple CMake build and example usage.
• JSON configuration initialization: Easily set up logger sinks via a JSON config file

Usage Example

In your CMakeLists.txt:

Add Logger to Your Project

You can include this Logger project as a subdirectory in your own CMake project. For example, if you clone or include it as a git submodule under submodules/Logger, you can do:

In your top-level CMakeLists.txt

add_subdirectory(submodules/Logger)

Link Logger to Your Executable/Library

Next, link the Logger library to your target. For instance:

target_link_libraries(MyApp PRIVATE Logger)

Because the Logger uses a PUBLIC include for its headers, you do not need extra include_directories for the Logger — they are automatically made available to your target.

In your code:

Programmatic Initialization

You can manually add sinks using the provided builder methods:

#include "Logger.h"

int main()
{
    // Setup file output with custom options
    logging::addFileOutput()
        .setFilename("TestLog.log")
        .setLevel(LogLevel::Info)
        .setMaxFileSize(20_MB)
        .setRotateOnSession(true);

    // Setup console output with custom level
    logging::addConsoleOutput().setLevel(LogLevel::Debug);

    LOG_INFO("Hello logger, the answer is: {}", 42);

    return 0;
}

JSON Configuration Initialization

Alternatively, you can initialize the logger via a JSON configuration file. Create a JSON file (e.g. logger_config.json) with the following structure:

{
    "sinks": [
        {
            "type": "console",
            "level": "debug",
            "max_skip_duration": 0,
            "pattern": "[%Y-%m-%d %H:%M:%S.%e] [%l] %v"
        },
        {
            "type": "file",
            "level": "info",
            "max_skip_duration": 0,
            "file_name": "logs/app.log",
            "max_file_size": "10_MB",
            "max_files": 3,
            "rotate_on_session": true
        }
    ]
}

Then in your code initialize the logger using:

#include "Logger.h"

int main()
{
    // Initialize logger with JSON configuration.
    // Missing settings will be replaced with default values.
    logging::initializeLogger("logger_config.json");

    LOG_INFO("Logger initialized using JSON configuration!");

    return 0;
}

This approach leverages nlohmann json (integrated via CPM) to parse the configuration file and set up the sinks accordingly. If a key is missing, a sensible default will be used.

Overriding JSON Configuration Keys

This project defines the JSON key names (used in the configuration file) as CMake Cache variables. This means that when you include Logger as a subdirectory in your project, you can easily override these defaults without modifying the Logger source code.

How to override

Before adding the Logger subdirectory in your parent project's CMakeLists.txt, set the desired values for the JSON keys. For example:

# Override default JSON key names
set(LOGGER_CONFIG_SINK "custom_sinks" CACHE STRING "JSON key for logger sinks")
set(LOGGER_CONFIG_LEVEL "custom_level" CACHE STRING "JSON key for log level")
# ...set other keys as needed

add_subdirectory(path/to/Logger)

Alternatively, you can override these values on the command line when configuring your project:

cmake -DLOGGER_CONFIG_SINK="custom_sinks" -DLOGGER_CONFIG_LEVEL="custom_level" <path-to-your-project>

Default values

If not otherwise specified, the logger will provide default values:

Console Sink Defaults

• Log Level : info
• Max Skip Duration : 0 (microseconds)
• Pattern : [%Y-%m-%d %H:%M:%S.%e] [%l] %v

File Sink Defaults

• Log Level : info
• Max Skip Duration : 0 (microseconds)
• File Name : default.log
• Max File Size : 10 MB
• Max Files : 3
• Rotate on session : false

MSVC Sink Defaults (Windows Only)

• Log Level : info
• Max Skip Duration : 0 (microseconds)
• Check For Debugger : false

Notes

• Update CMakeLists.txt or build.py according to your needs.
• Requires C++20 and CMake ≥ 3.25.
• By default, logs are written at Info level to the configured sinks.
• The spdlog library is included via CPM in the libs directory.

Enjoy streamlined logging with SPDLog!