Logger - Header-Only C++ Logging Library

Version: 1.0
Author: tadeyemo32
License: MIT

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Overview

Logger is a thread-safe, header-only C++ logging library that follows the Singleton design pattern and designed for professional applications. It supports multiple log formats, runtime debug control, and automatic log rotation. The library is easy to integrate and requires no external dependencies beyond the C++17 standard library.

Features:

• Header-only, simple to include.
• Thread-safe for concurrent logging in multithreaded applications.
• Supports multiple log formats: TXT, CSV, JSON, XML.
• Configurable debug mode for console output.
• Automatic log rotation based on file size.
• Singleton pattern ensures a single logger instance per application.
• Easy runtime toggle for debug/console logging.
• Logs include timestamps, log levels, and serialized data for future parsing.

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Installation

Simply include the header in your project:

#include "logger.h"

Ensure the library is in your include path or project directory. No compilation or linking is required.

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Usage

Basic Example

#include "logger.h"

int main() {
    // Create logger instance: filename, format, max size in MB (optional), debug mode (optional)
    auto &logger = Log::Logger::getInstance("server_logs", Log::FormatType::JSON, 5, true);

    logger.log("Server started", Log::LogType::INFO);
    logger.log("New connection received", Log::LogType::DEBUG);

    // Change debug status at runtime
    logger.setDebugStatus(false);
    logger.log("Debug output disabled", Log::LogType::INFO);

    return 0;
}

Multiple Formats

auto &txtLogger = Log::Logger::getInstance("app_txt", Log::FormatType::TXT,true,5);
auto &csvLogger = Log::Logger::getInstance("app_csv", Log::FormatType::CSV, 10);

• TXT: [timestamp] [level] message
• CSV: timestamp,level,message
• JSON: { "timestamp": "...", "log_type": "...", "message": "..." }
• XML: <log><timestamp>...</timestamp><type>...</type><message>...</message></log>

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API Reference

Logger

static Logger& getInstance(const std::string &filename, FormatType format, size_t maxSizeMB = 10, bool debug = false)

Get the singleton instance of Logger.

• filename: Name of the log file (without extension)
• format: FormatType (TXT, CSV, JSON, XML)
• maxSizeMB: Maximum log file size in MB before rotation (optional)
• debug: Enable/disable console output (optional)

void log(const std::string &message, LogType type)

Logs a message with the specified severity. Automatically includes timestamp.

void setDebugStatus(bool status)

Toggle debug output to the console at runtime.

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LogType Enum

• INFO
• DEBUG
• WARNING
• ERROR
• CRITICAL
• UNKNOWN

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FormatType Enum

• TXT
• CSV
• JSON
• XML

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Example Output

JSON Log Example:

{
  "timestamp": "2025-08-26 05:21:00",
  "log_type": "Info",
  "message": "Logger initialized"
}

TXT Log Example:

[2025-08-26 05:21:00] [Info] Logger initialized

CSV Log Example:

2025-08-26 05:21:00,Info,Logger initialized

XML Log Example:

<log>
  <timestamp>2025-08-26 05:21:00</timestamp>
  <type>Info</type>
  <message>Logger initialized</message>
</log>

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Notes

• Singleton ensures only one instance exists across all files.
• Thread-safe with internal mutex locking.
• File rotation automatically renames old logs when exceeding maxSizeMB.
• Console debug mode is optional and can be toggled at runtime.

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License

This project is licensed under the MIT License. See LICENSE for details.