systwit.c

/*
 * A daemon that reads the /proc/stats file, calculates the cpu usage
 * percentage and writes it to syslog.
 *
 * Copyright (C) 2015-2016 Sebastian Glinski <sebastian.glinski@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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include <string.h>
#include <sys/types.h>


#define STAT_FILE "/proc/stat"
#define READ_SIZE 200
#define SLEEP_CYCLE 5


typedef struct {
  u_int32_t user;         /* Time spent in user mode */
  u_int32_t nice;         /* Time spent in user mode with low priority (nice) */
  u_int32_t systm;        /* Time spent in system mode */
  u_int32_t idle;         /* Time spent in the idle task */
  u_int32_t iowait;       /* Time waiting for I/O to complete */
  u_int32_t irq;          /* Time servicing interrupts */
  u_int32_t softirq;      /* Time servicing softirqs */
  u_int32_t steal;        /* Stolen time, which is the time spent in other operating systems when running in a virtualized environment */
  u_int32_t guest;        /* Time spent running a virtual CPU for guest operating systems under the control of the Linux kernel */
  u_int32_t guest_nice;   /* Time spent running a niced guest */
} cpu_stats;

cpu_stats cur_stat, pre_stat;

void read_stats_file(void);
cpu_stats read_cpu_stats(char[]);
float calculate_percentage(void);

int main(int argc, char const *argv[]) {
  pid_t pid, sid;

  /* Fork off the parent process */
  if((pid = fork()) < 0) {
    exit(EXIT_FAILURE);
  }

  /* If we got a good pid then we
   * can exit the parent process
   */
  if(pid > 0) {
    exit(EXIT_SUCCESS);
  }

  /* Change the file mode mask to 0
   * so we will have full access to the
   * files generated by the daemon.
   */
  umask(0);

  /* Connect to the syslog daemon */
  openlog(argv[0], LOG_NOWAIT|LOG_PID, LOG_USER);
  syslog(LOG_NOTICE, "Successfully started daemon");

  /* Create a new session id for the
   * child process
   */
  sid = setsid();
  if(sid < 0) {
    syslog(LOG_ERR, "Could not create process group\n");
    exit(EXIT_FAILURE);
  }

  /* Change the working directory
   * where the daemon operates in
   */
  if((chdir("/")) < 0) {
    syslog(LOG_ERR, "Could not change working directory to /\n");
    exit(EXIT_FAILURE);
  }

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

  /* The main loop where the daemon runs in */
  while(1) {
    read_stats_file();
    syslog(LOG_INFO, "CPU Percentage: %f", calculate_percentage());
    sleep(5);
  }

  close_syslog();

  return 0;
}

void read_stats_file(void) {
  FILE *file;
  file = fopen(STAT_FILE, "r");
  char puffer[READ_SIZE];
  int t_idle = 0, t_iowait = 0;

  /* Read the first line of the stat file */
  fgets(puffer, READ_SIZE, file);

  /* Keep the statistics from the last run
   * in pre_stat
   */
  pre_stat = cur_stat;
  cur_stat = read_cpu_stats(puffer);

  /*
  syslog(LOG_INFO, "%u - %u - %u - %u - %u - %u - %u - %u - %u - %u", pre_stat.user, pre_stat.nice, pre_stat.systm, pre_stat.idle, pre_stat.iowait, pre_stat.irq, pre_stat.softirq, pre_stat.steal, pre_stat.guest, pre_stat.guest_nice);
  syslog(LOG_INFO, "%u - %u - %u - %u - %u - %u - %u - %u - %u - %u", cur_stat.user, cur_stat.nice, cur_stat.systm, cur_stat.idle, cur_stat.iowait, cur_stat.irq, cur_stat.softirq, cur_stat.steal, cur_stat.guest, cur_stat.guest_nice);
  */

  fclose(file);
}

cpu_stats read_cpu_stats(char c[]) {
  cpu_stats s;
  char *tokens[15];
  char *t;
  int i = 0;

  /* Skip the first token which is the string 'cpu' */
  strtok(c, " ");

  /* Read the tokens from the first cpu-line and parse
   * them into the structure
   */
  t = strtok(NULL, " ");
  while(t != NULL) {
    sscanf(t, "%u", &((u_int32_t*)&s)[i]);
    t = strtok(NULL, " ");
    i++;
  }

  return s;
}

float calculate_percentage(void) {
  u_int32_t prevIdle = pre_stat.idle + pre_stat.iowait;
  u_int32_t idle = cur_stat.idle + cur_stat.iowait;

  u_int32_t prevNonIdle = pre_stat.user + pre_stat.nice + pre_stat.systm + pre_stat.irq + pre_stat.softirq + pre_stat.steal;
  u_int32_t nonIdle = cur_stat.user + cur_stat.nice + cur_stat.systm + cur_stat.irq + cur_stat.softirq + cur_stat.steal;

  u_int32_t totald = (idle + nonIdle) - (prevIdle + prevNonIdle);
  u_int32_t idled = idle - prevIdle;

  /* float CPU_Percentage = (totald - idled)/(float)totald; */

  return (totald - idled) / (float)totald;
}