Fastlog: A Lightweight Logging Library for C

Fastlog is a simple and efficient logging library for C, designed to provide flexible logging capabilities with minimal overhead. It supports logging to both files and syslog, making it suitable for a wide range of applications.

Features

• File Logging: Log messages to a file with automatic file handling.
• Syslog Integration: Fallback to syslog if file logging fails or is disabled.
• Thread-Safe: Designed to be used in multi-threaded environments.
• Customizable: Supports custom log paths, error handling, and message formatting.
• Lightweight: Minimal dependencies and low resource usage.
• Cross-Platform: Works on Linux and macOS (including Apple Silicon).

Installation

Prerequisites

• A C compiler (e.g., gcc, clang)
• make (for building the project)

Building from Source

1. Clone the repository:

   git clone https://github.com/yourusername/fastlog.git
   cd fastlog

2. Build the library and test program:

   make

3. (Optional) Install the library system-wide:

   sudo make install

   On macOS, the library and headers will be installed to /usr/local/lib and /usr/local/include/flog, respectively.

4. Run the test program to verify the installation:

   ./test
   

Usage

Basic Logging

To use Fastlog in your project, include the flog.h header and link against the libflog library.

#include "flog.h"

 int main(void) {
     // Set the log file path
     logpath("/tmp/myapp.log");

     // Log a message
     flog("Application started.");

     // Log formatted messages
     flog("User ID: %d, Username: %s", 1234, "john_doe");

     // Close the log file
     closelogfile();

     return 0;
 }

Advanced Features

• Fallback to Syslog: If the log file cannot be opened, messages are automatically written to syslog.

• Error Handling: Check the return value of logpath to handle errors gracefully.

• Custom Log Paths: Dynamically change the log file path at runtime.

Example: Error Handling

if (logpath("/invalid/path/to/logfile.log") == LOG_ERROR) {
    flog("Failed to open log file. Falling back to syslog.");
}

API Reference

Functions

• void flog(const char* output, ...)

  Logs a formatted message to the current log file or syslog.

• int logpath(const char* logfile)

  Sets the log file path. Returns NO_ERROR on success or LOG_ERROR on failure.

• void closelogfile(void)

  Closes the current log file.

• char* getlogpath(void)

  Returns the current log file path.

• void flushlog(void) Flushes the log file buffer.

• int openlogfile(char* logfilename)

  Opens a log file. Used internally by logpath.

• void writesyslog(const char* format, ...)

  Writes a message to syslog. Used internally as a fallback.