deamon.c

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/***************************************************************************
                          deamon.c  -  description
                             -------------------
    begin                : Thu Sep 27 08:08:03 EET 2001
    copyright            : (C) 2001 by Petri Turunen
    email                : [e-mail]
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif


#include<stdio.h>
#include <unistd.h>  //for fork,getrlimit
#include <sys/types.h> //for umask, open
#include <sys/stat.h> //for umask, open
#include <fcntl.h> //for umask, open
#include <sys/time.h> //for getrlimit
#include <sys/resource.h> //for getrlimit
#include <stdlib.h> // for exit
#include "linux_mond.h"

extern char PIDDIR[]; //defined in linux_mon.c

int make_deamon(void) //Make me daemon
{

        struct rlimit resourceLimit = { 0 };
        int status = -1;
        int fileDesc = -1;
        int i = 0;
        FILE *pid_file;
	char pidfile[30]="\0";

        status = fork();
    switch (status)
    {
    case -1:
        slog(2,"deamon.c: fork() failed in make_deamon");
        exit(-1);
    case 0: /* child process */
        break;
    default: /* parent process */
        exit(0);
    }
    /*
     * child process
     */
    resourceLimit.rlim_max = 0;
    status = getrlimit(RLIMIT_NOFILE,
        &resourceLimit);
    if (-1 == status) /* shouldn't happen */
    {
        slog(2,"deamon.c: getrlimit() failed in make_deamon");
        exit(-1);
    }
    if (0 == resourceLimit.rlim_max)
    {
	slog(2,"deamon.c: Error max number of open file descriptors is 0!!");
        exit(-1);
    }

    for (i = 0; i < resourceLimit.rlim_max; i++)
    {
        (void) close(i);
    }
    status = setsid();
    if (-1 == status)
    {
        slog(2,"deamon.c: setsid() failed in make_deamon");
        exit(-1);
    }
    status = fork();
    switch (status)
    {
    case -1:
        slog(2,"deamon.c: fork() failed in make_deamon");
        exit(-1);
    case 0: /* (second) child process */
        break;
    default: /* parent process */
        exit(0);
    }
    /*
     * now we are in a new session and process
     * group than process that started the
     * daemon. We also have no controlling
     * terminal */
    chdir("/tmp/");
    if(status != 0)
    {
     slog(2,"Failed to change directory to /tmp. %s",strerror(errno));
     printf("Failed to change directory to /tmp. %s\n",strerror(errno));
     exit(-1);
    }
    umask(0);
    fileDesc = open("/dev/null", O_RDWR);/* stdin */
    (void) dup(fileDesc);       /* stdout */
    (void) dup(fileDesc);       /* stderr */

    strcat(pidfile,PIDDIR);
    strcat(pidfile,"/linux_mond.pid");
    pid_file = fopen(pidfile,"w");
    if(pid_file==NULL)
     slog(2,"deamon.c: Error while opening %s. %s",pidfile, strerror(errno));
    else {
     fprintf(pid_file, "%d",getpid());
     fclose(pid_file);
    }
    /*
     * the rest of the daemon code executes in
     * this environment
     */
     return 0;
}