/**

 * daemon.c

 * Copyright (C) 2008 Markus Broeker

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <time.h>

#include <fcntl.h>

#include <unistd.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <signal.h>

#define      MAXLEN 80

#define    TIME_OUT 60

#define  INPUT_FILE "/proc/meminfo"

#define OUTPUT_FILE "/tmp/meminfo.log"

#define   LOCK_FILE "/tmp/.daemon.lock"

void check (int fd, char *buffer)

{

    char response[1024];

    char time_stamp[40];

    int len;

    time_t t;

    t = time (NULL);

    strftime (time_stamp, sizeof (time_stamp), "%a %d %T", localtime (&t));

    len = snprintf (response, sizeof (response), "%s %s", time_stamp, buffer);

    if (write (fd, response, len) == -1)

        perror ("write");

}

void sigproc ()

{

    if (unlink (LOCK_FILE) == 0)

        exit (EXIT_SUCCESS);

    exit (EXIT_FAILURE);

}

void sanity_check (int argc, char **argv)

{

    struct stat st;

    int fd;

    if (stat (INPUT_FILE, &st) != 0) {

        perror (INPUT_FILE);

        exit (EXIT_FAILURE);

    }

    if (argc == 2) {

        if (!strcmp (argv[1], "-h")) {

            printf ("Usage: %s [-f|-h]\n", argv[0]);

            printf ("Report bugs to mbroeker@largo.homelinux.org\n");

            exit (EXIT_SUCCESS);

        } else if (!strcmp (argv[1], "-f")) {

            if (unlink (LOCK_FILE) != 0)

                exit (EXIT_FAILURE);

        } else {

            fprintf (stderr, "Unknown Option %s\n", argv[1]);

            exit (EXIT_FAILURE);

        }

    }

    if (stat (LOCK_FILE, &st) < 0) {

        if ((fd = open (LOCK_FILE, O_WRONLY | O_CREAT, 0)) < 0) {

            perror (LOCK_FILE);

            exit (EXIT_FAILURE);

        }

        close (fd);

    } else {

        fprintf (stderr, "%s is already running\n", argv[0]);

        exit (EXIT_FAILURE);

    }

    fprintf (stderr, "%s monitors %s every %d seconds into %s\n", argv[0], INPUT_FILE, TIME_OUT, OUTPUT_FILE);

}

int main (int argc, char **argv)

{

    FILE *fin;

    static char buffer[MAXLEN];

    int fd;

    sanity_check (argc, argv);

    if (daemon (0, 0) == -1) {

        perror ("daemon");

        return EXIT_FAILURE;

    }

    signal (SIGTERM, sigproc);

    for (;;) {

        if ((fd = open (OUTPUT_FILE, O_WRONLY | O_CREAT, 0644)) < 0)

            return EXIT_FAILURE;

        if ((fin = fopen (INPUT_FILE, "r")) == NULL)

            return EXIT_FAILURE;

        while (fgets (buffer, sizeof (buffer), fin))

            check (fd, buffer);

        fclose (fin);

        close (fd);

        sleep (TIME_OUT);

    }

    return EXIT_SUCCESS;

}