mbpfan/src/daemon.c

/**
 *  Copyright (C) 2012  Peter Lombardo <http://peterlombardo.wikidot.com/linux-daemon-in-c>
 *  Modifications (2012) by Daniel Graziotin <dgraziotin@task3.cc>
 *  Modifications (2012) by Ismail Khatib <ikhatib@gmail.com>
 *
 *  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 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.
 *
 */


#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <syslog.h>
#include <string.h>
#include <assert.h>
#include <signal.h>
#include <unistd.h>
#include "mbpfan.h"
#include "global.h"

int write_pid(int pid)
{
  FILE *file = NULL;
  file = fopen(program_pid, "w");
  if(file != NULL)
    {
      fprintf(file, "%d", pid);
      fclose(file);
      return 1;
    }
  else
    {
      return 0;
    }
}

int read_pid()
{
  FILE *file = NULL;
  int pid = -1;
  file = fopen(program_pid, "r");
  if(file != NULL)
    {
      fscanf(file, "%d", &pid);
      fclose(file);
      return pid;
    }
  return -1;
}

int delete_pid()
{
  return remove(program_pid);
}


void signal_handler(int signal)
{

  switch(signal)
    {
    case SIGHUP:
      //TODO: restart myself
      syslog(LOG_WARNING, "Received SIGHUP signal.");
      delete_pid();
      exit(0);
      break;
    case SIGTERM:
      syslog(LOG_WARNING, "Received SIGTERM signal.");
      delete_pid();
      //TODO: free resources
      exit(0);
      break;
    case SIGINT:
      syslog(LOG_WARNING, "Received SIGINT signal.");
      delete_pid();
      //TODO: free resources
      exit(0);
    default:
      syslog(LOG_WARNING, "Unhandled signal (%d) %s", signal, strsignal(signal));
      break;
    }
}

void go_daemon(void (*fan_control)())
{

  // Setup signal handling before we start
  signal(SIGHUP, signal_handler);
  signal(SIGTERM, signal_handler);
  signal(SIGINT, signal_handler);

  syslog(LOG_INFO, "%s starting up", program_name);

  // Setup syslog logging - see SETLOGMASK(3)
  if(verbose)
    {
      setlogmask(LOG_UPTO(LOG_DEBUG));
      openlog(program_name, LOG_CONS | LOG_NDELAY | LOG_PERROR | LOG_PID, LOG_USER);
    }
  else
    {
      setlogmask(LOG_UPTO(LOG_INFO));
      openlog(program_name, LOG_CONS, LOG_USER);
    }


  pid_t pid_slave;
  pid_t sid_slave;

  if (daemonize)
    {

      pid_slave = fork();
      if (pid_slave < 0)
        {
          exit(EXIT_FAILURE);
        }
      if (pid_slave > 0)
        {
          // kill the father
          exit(EXIT_SUCCESS);
        }

      umask(0022);

      // new sid_slave for the child process
      sid_slave = setsid();
      if (sid_slave < 0)
        {
          exit(EXIT_FAILURE);
        }

      if ((chdir("/")) < 0)
        {
          exit(EXIT_FAILURE);
        }



      /* Close out the standard file descriptors */
      close(STDIN_FILENO);
      close(STDOUT_FILENO);
      close(STDERR_FILENO);
    }


  int current_pid = getpid();

  if (read_pid() == -1)
    {
      if (verbose)
        {
          printf("Writing a new .pid file with value %d at: %s\n", current_pid, program_pid);
          syslog(LOG_INFO, "Writing a new .pid file with value %d at: %s", current_pid, program_pid);
        }
      if (write_pid(current_pid) == 0)
        {
          syslog(LOG_ERR, "Can not create a .pid file at: %s. Aborting", program_pid);
          if (verbose)
            {
              printf("ERROR: Can not create a .pid file at: %s. Aborting\n", program_pid);
            }
          exit(EXIT_FAILURE);
        }
      else
        {
          if (verbose)
            {
              printf("Successfully written a new .pid file with value %d at: %s\n", current_pid, program_pid);
              syslog(LOG_INFO, "Successfully written a new .pid file with value %d at: %s", current_pid, program_pid);
            }
        }
    }
  else
    {
      syslog(LOG_ERR, "A previously created .pid file exists at: %s. Aborting", program_pid);
      if (verbose)
        {
          printf("ERROR: a previously created .pid file exists at: %s.\n Aborting\n", program_pid);
        }
      exit(EXIT_FAILURE);
    }


  fan_control();

  if(daemonize)
    {
      syslog(LOG_INFO, "%s daemon exiting", program_name);
    }

  return;
}