#include <stdio.h>

#include <fcntl.h>

#include <signal.h>

#include <unistd.h>

#include <stdlib.h>

#include <string.h>

#include <sys/types.h>

#include <sys/stat.h>

#define RUNNING_DIR "tmp"

#define LOCK_FILE "tmp/daemond.lock"

#define LOG_FILE "tmp/daemond.log"

/*

 *       daemon.c

 *

 *       Copyright 2010 Vasudev Kamath <kamathvasudev@gmail.com>

 *     

 *       This program is free software; you can redistribute it and/or modify

 *       it under the terms of the GNU Lesser General Public License as published by

 *       the Free Software Foundation; either version 3 of the License, or

 *       (at your option) any later version.

 *     

 *       This program is distributed in the hope that it will be useful,

 *       but WITHOUT ANY WARRANTY; without even the implied warranty of

 *       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *       GNU General Public License for more details.

 *      

 *       You should have received a copy of the GNU General Public License

 *       along with this program; if not, write to the Free Software

 *       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

 *       MA 02110-1301, USA.

 */

void log_signal_message(char *message){

    FILE *logfile;

    logfile = fopen(LOG_FILE,"a");

    if(!logfile) return;

    fprintf(logfile,"%s",message);

    fclose(logfile);

}

int lfp;

void close_lock_file()

{

    close(lfp);

    remove(LOCK_FILE);

}

void kamathvasudev_daemonize(){

    int pid;

    int i;

    char str[10];

    pid = getppid();

    if(pid == 1) return;

    pid = fork();

    if(pid < 0) exit(1);

    if(pid > 0) exit(0);

    setsid();

    /*

     * Double fork method

     */

    pid = fork();

    if(pid < 0) exit(1);

    if(pid > 0) exit(0);

    for(i = getdtablesize(); i >= 0; --i) close(i);

    lfp = open("/dev/null",O_RDWR);

    dup(lfp);

    dup(lfp);

    umask(022);

    lfp = open(LOCK_FILE,O_RDWR|O_CREAT,0640);

    if(lfp < 0) { log_signal_message("daemond is allready running !\n");exit(1); }

    if(lockf(lfp,F_TLOCK,0) < 0) { log_signal_message("daemond is allready running\n");exit(1); }

    sprintf(str,"%d\n",getpid());

    write(lfp,str,strlen(str));

    atexit(close_lock_file);

}

void daemonize()

{

    pid_t pid;

    char str[10];

    /*

     * use unistd.h function

     *   - do change to root directory

     *   - close std streams

     */

    daemon(1, 0);

    /*

     * Double fork method

     */

    pid = fork();

    if(pid < 0) exit(1);

    if(pid > 0) exit(0);

    umask(022);

    lfp = open(LOCK_FILE,O_RDWR|O_CREAT,0640);

    if(lfp < 0) { log_signal_message("daemond is allready running !\n");exit(1); }

    if(lockf(lfp,F_TLOCK,0) < 0) { log_signal_message("daemond is allready running\n");exit(1); }

    sprintf(str,"%d\n",getpid());

    write(lfp,str,strlen(str));

    atexit(close_lock_file);

}