/* procfs.c */

/* Read in proc file system data for PID given on command line */

#define _STRUCTURED_PROC 1   /* THIS IS IMPORTANT */

#include <procfs.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>

psinfo_t  info;
prusage_t usage;

int main(
int argc,
char **argv)
{
   char name[30];
   char base[30];
   int  fd;
   int  len;

/* Ensure that user provided a command line parameter */

   if (argc < 2)
   {
      printf("Usage is a.out pid \n");
      printf("Goodbye \n");
      exit(1);
   }

/* If user supplied 123 as a pid, we construct the string  */
/* /proc/123 here                                          */

   strcpy(base, "/proc/");
   strcat(base, argv[1]);

/* Copy /proc/123 to name and then create /proc/123/psinfo */

   strcpy(name, base);
   strcat(name, "/psinfo");

/* Attempt to open the file */

   fd = open(name, O_RDONLY);
   if (fd < 0)
   {
      printf("Attempt to open %s failed \n", name);
      exit(1);
   }

/* Read data into the structure that maps it and verify length read */

   len = read(fd, &info, sizeof(info));
   if (len != sizeof(info))
   {
      printf("Length error expected %d got %d \n", sizeof(info), len);
   }
   close(fd);

/* Print required fields... The only way to know the names of the   */
/* required structure elements is to READ /usr/include/sys/procfs.h */

   printf("Program name is:     %12s \n", info.pr_fname);

/* Repeat the process for the usage structure */

   strcpy(name, base);
   strcat(name, "/usage");
   fd = open(name, O_RDONLY);
   len = read(fd, &usage, sizeof(usage));
   if (len != sizeof(usage))
   {
      printf("Length error expected %d got %d \n", sizeof(usage), len);
   }
   close(fd);

   printf("User CPU time:       %12d.%03d \n",
            usage.pr_utime.tv_sec, usage.pr_utime.tv_nsec / 1000000);


}