daemon.c
author Markus Bröker <mbroeker@largo.dyndns.tv>
Fri, 27 Dec 2013 16:00:09 +0100
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permissions -rw-r--r--
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/**
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 * daemon.c
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 * Copyright (C) 2008 Markus Broeker
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <signal.h>
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#define      MAXLEN 80
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#define    TIME_OUT 60
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#define  INPUT_FILE "/proc/meminfo"
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#define OUTPUT_FILE "/tmp/meminfo.log"
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#define   LOCK_FILE "/tmp/.daemon.lock"
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void check (int fd, char *buffer)
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{
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    char response[1024];
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    char time_stamp[40];
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    int len;
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    time_t t;
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    t = time (NULL);
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    strftime (time_stamp, sizeof (time_stamp), "%a %d %T", localtime (&t));
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    len = snprintf (response, sizeof (response), "%s %s", time_stamp, buffer);
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    if (write (fd, response, len) == -1)
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        perror ("write");
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}
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void sigproc ()
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{
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    if (unlink (LOCK_FILE) == 0)
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        exit (EXIT_SUCCESS);
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    exit (EXIT_FAILURE);
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}
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void sanity_check (int argc, char **argv)
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{
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    struct stat st;
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    int fd;
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    if (stat (INPUT_FILE, &st) != 0) {
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        perror (INPUT_FILE);
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        exit (EXIT_FAILURE);
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    }
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    if (argc == 2) {
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        if (!strcmp (argv[1], "-h")) {
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            printf ("Usage: %s [-f|-h]\n", argv[0]);
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            printf ("Report bugs to mbroeker@largo.homelinux.org\n");
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            exit (EXIT_SUCCESS);
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        } else if (!strcmp (argv[1], "-f")) {
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            if (unlink (LOCK_FILE) != 0)
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                exit (EXIT_FAILURE);
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        } else {
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            fprintf (stderr, "Unknown Option %s\n", argv[1]);
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            exit (EXIT_FAILURE);
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        }
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    }
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    if (stat (LOCK_FILE, &st) < 0) {
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        if ((fd = open (LOCK_FILE, O_WRONLY | O_CREAT, 0)) < 0) {
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            perror (LOCK_FILE);
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            exit (EXIT_FAILURE);
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        }
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        close (fd);
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    } else {
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        fprintf (stderr, "%s is already running\n", argv[0]);
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        exit (EXIT_FAILURE);
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    }
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    fprintf (stderr, "%s monitors %s every %d seconds into %s\n", argv[0], INPUT_FILE, TIME_OUT, OUTPUT_FILE);
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}
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int main (int argc, char **argv)
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{
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    FILE *fin;
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    static char buffer[MAXLEN];
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    int fd;
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    sanity_check (argc, argv);
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    if (daemon (0, 0) == -1) {
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        perror ("daemon");
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        return EXIT_FAILURE;
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    }
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    signal (SIGTERM, sigproc);
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    for (;;) {
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        if ((fd = open (OUTPUT_FILE, O_WRONLY | O_CREAT, 0644)) < 0)
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            return EXIT_FAILURE;
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        if ((fin = fopen (INPUT_FILE, "r")) == NULL)
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            return EXIT_FAILURE;
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        while (fgets (buffer, sizeof (buffer), fin))
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            check (fd, buffer);
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        fclose (fin);
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        close (fd);
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        sleep (TIME_OUT);
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    }
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    return EXIT_SUCCESS;
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}