From owner-freebsd-hackers  Thu Jul 15 10: 1:58 1999
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Date: Thu, 15 Jul 1999 11:00:11 -0600 (MDT)
From: "Ronald G. Minnich" <rminnich@acl.lanl.gov>
To: hackers@freebsd.org
Subject: Another take on /proc statistics (joke of the day)
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I thought this amusing. 

Take the following program, designed to suck stats out of /proc for the
network devices:

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

main()
{
  char stuff[4096];
  int fd = open("/proc/net/dev", 0);

  while(1)
    {
      int amount = read(fd, stuff, sizeof(stuff));
      if (amount > 0)
        write(1, stuff, amount);
      sleep(1);
      lseek(fd, (off_t) 0, SEEK_SET);
    }

}

Run this on linux, and you'll get the same values for all the stats. 

how to make it work right? 

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

main()
{
  char stuff[4096];

  while(1)
    {
      int fd = open("/proc/net/dev", 0);
      int amount;
      amount = read(fd, stuff, sizeof(stuff));
      if (amount > 0)
        write(1, stuff, amount);
      close(fd);
      sleep(1);
    }
  
}

What are the implications of this? Well, if you have an rstatd that uses
/proc for statistics, it will have to (for every request)  open the status
files, read them, and close them. Net result: very very poor performance
for an rstatd (not even counting the fact that the rstatd has to parse
formatted output back to a binary format ...)

ron
p.s. the rstatd I have for redhat does indeed read stats out of /proc ...




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