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;
}