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// Daemon Demo
// Demo code for daemon programs
// Author: guitat 
// Date: 18/01/2014
// File name: daemondemo.c
// Features: 
// 1) start, stop and status function 
// 2) pid file management 
// 3) system log implemented

#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <stdlib.h>
#include <libconfig.h>
#include <unistd.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <syslog.h>

// change these value as well
const char *filepid="/run/daemondemo.pid";
const char *logname="daemondemo";

void signal_callback_handler(int signum){
	pid_t cpid;
	FILE *cfpid;
	if( access( filepid, F_OK ) != -1 ){
		cfpid=fopen(filepid,"r");
		fscanf(cfpid, "%d\n", &cpid);
		fclose(cfpid);
		if (cpid==getpid()){
			closelog();
			remove(filepid);
			abort();
		}
	}
}

static void daemonize(){

	pid_t dpid;
	FILE *dfpid;

	/* Fork off the parent process */
	dpid = fork();

	/* An error occurred */
	if (dpid < 0)
		exit(EXIT_FAILURE);

	/* Success: Let the parent terminate */
	if (dpid > 0)
		exit(EXIT_SUCCESS);

	/* On success: The child process becomes session leader */
	if (setsid() < 0)
		exit(EXIT_FAILURE);

	/* Catch, ignore and handle signals */
	//TODO: Implement a working signal handler */
	//signal(SIGCHLD, SIG_IGN);
	//signal(SIGHUP, SIG_IGN);

	/* Fork off for the second time*/
	dpid = fork();

	/* An error occurred */
	if (dpid < 0)
		exit(EXIT_FAILURE);

	/* Success: Let the parent terminate */
	if (dpid > 0)
		exit(EXIT_SUCCESS);

	/* Set new file permissions */
	umask(0);

	/* Change the working directory to the root directory */
	/* or another appropriated directory */
	chdir("/");

	/* Close all open file descriptors */
	int x;
	for (x = sysconf(_SC_OPEN_MAX); x>0; x--)
	{
		close (x);
	}
		
	// Saving pid in the .pid file
	dfpid=fopen(filepid,"w");
	fprintf(dfpid, "%d\n", getpid());
	fclose(dfpid);

	/* Open the log file */
	openlog (logname, LOG_PID, LOG_DAEMON);

	signal(SIGINT, signal_callback_handler);
	signal(SIGHUP, signal_callback_handler);
	signal(SIGTERM, signal_callback_handler);
	signal(SIGQUIT, signal_callback_handler);

}




int main (int argc, char **argv)
{
	FILE *fpid;
	pid_t pid=0;

	if ( argc != 2 ){
		printf ("Usage: %s [start|stop|status]\n", argv[0]);
		return 1;
	}else{
		if (!strcmp(argv[1],"start")){
			if( access( filepid, F_OK ) != -1 ) {
				// pid file exist: daemon is running
				printf("Daemon is already running.\n");
				
			} else {
				// pid file doesn't exist: daemon is stopped
				daemonize();

				/*------------------------------------------------*/
				/* INFINITE LOOP WRITE THE BODY OF PROGRAM INSIDE */
				/*------------------------------------------------*/
				for(;;){
					//body of program



				}
			}
		}
		if (!strcmp(argv[1],"stop")){
			if( access( filepid, F_OK ) != -1 ) {
    				// pid file exist: daemon is running
				printf("Stopping daemon...");
				fpid=fopen(filepid,"r");
				fscanf(fpid, "%d\n", &pid);
				fclose(fpid);
				syslog (LOG_NOTICE, "stopping daemon");
				closelog();
				kill(pid, SIGINT);
				printf(" stopped!\n");

			} else {
				// pid file doesn't exist: daemon is stopped
				printf("Daemon is not running.\n");
			}
			
			
		}
		if (!strcmp(argv[1],"status")){
			if( access( filepid, F_OK ) != -1 ) {
				// pid file exist: daemon is running
				fpid=fopen(filepid,"r");
				fscanf(fpid, "%d\n", &pid);
				fclose(fpid);
				printf("Daemon is running with pid: %d.\n",pid); 
				
			} else {
				// pid file doesn't exist: daemon is stopped
				printf("Daemon is stopped.\n");
			}
		}
	}
	return(EXIT_SUCCESS);  
}

Code: Select all

gcc -Wall daemondemo.c -o daemondemo