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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