Logging wrapper for printf. Uses shell commands to add some colours. Define loglevel in line 8 and output file in line 17 (replace stdout).

logging.c

/**
 * implements the logging functions
 */
#include "logging.h"

enum{Debug, Info, Warning, Error, Fatal, Off};
//define the loglevel here
int loglevel = Debug;


/**
 * private function to wrap fprintf
 */
void printLog(char* message, char* logLevel) {
	//get current time
	time_t now = time(0);
	fprintf(stdout, "%s - %s: %s\n", ctime(&now), logLevel, message);
	fflush(stdout);
}

void logError(char* message, ...){
	if(loglevel <= Error){
		char* level = "\033[31mError\033[m";
		va_list args;
		va_start(args, message);
		char buffer[512];
		vsnprintf(buffer, sizeof(buffer), message, args);
		printLog(buffer, level);
		va_end(args);
	}
}

void logWarning(char* message, ...){
	if(loglevel <= Warning){
		char* level = "\033[33mWarning\033[m";
		va_list args;
		va_start(args, message);
		char buffer[512];
		vsnprintf(buffer, sizeof(buffer), message, args);
		printLog(buffer, level);
		va_end(args);
	}
}

void logInfo(char* message, ...){
	if(loglevel <= Info){
		char* level = "Info";
		va_list args;
		va_start(args, message);
		char buffer[512];
		vsnprintf(buffer, sizeof(buffer), message, args);
		printLog(buffer, level);
		va_end(args);
	}
}

void logDebug(char* message, ...){
	if(loglevel <= Debug){
		char* level = "\033[2mDebug\033[m";
		va_list args;
		va_start(args, message);
		char buffer[512];
		vsnprintf(buffer, sizeof(buffer), message, args);
		printLog(buffer, level);
		va_end(args);
	}
}

void logFatal(char* message, ...){
	if(loglevel <= Fatal){
		char* level = "\033[33mFatal\033[m";
		va_list args;
		va_start(args, message);
		char buffer[512];
		vsnprintf(buffer, sizeof(buffer), message, args);
		printLog(buffer, level);
		va_end(args);
	}
}

logging.h

#ifndef logging_h_
#define logging_h_

#include <stdio.h>
#include <time.h>
#include <stdarg.h>


void logError(char* message, ...);
void logWarning(char* message, ...);
void logInfo(char* message, ...);
void logDebug(char* message, ...);
void logFatal(char* message, ...);

#endif