[EMAIL PROTECTED] wrote:
On Sun, Jan 02, 2005 at 09:11:42PM +0300, Andrew P. wrote:
The ones that are the most interesting for me now is how to
write small daemons best and how to read ipfw info from a program.
Of course I can refresh my C skills and gain some Unix-coding knowledge
by reading a couple' thousand pages, but I don't feel like it's
necessary for what I want to write - just a basic statistics collector.
why not just go for a scripted solution in Perl or Python?
Well, I am going to dump all the ipfw counters to disk
(and process some data) in a loop of a single second.
Perl adds too much overhead for this task.
Should I explore FreeBSD source code or is there some solid piece of
documentation?
That's not necessary. If you want to write that in C, you'll have
to familiarize yourself with the popen(3) call for executing a program
and capturing its output. Then you need a few string processing functions
like str*(3) sscanf() etc... to parse the output (that's the tricky part).
Finally you will need a small example of a client and server in C that
uses the sockets API (that's pretty generic and not FreeBSD-specific at
all, just google for it). Combine all this and voila, you've got your
nice monitoring app in C.
As a matter of fact, I already do have a functional C program,
processing and dumping data, which it gets from stdin. So I have
a shell loop, invoking `ipfw show | c_program` every 10 seconds.
But it seems to be ineffective. What I'm thinking about is a
closer-to-real-time daemon dumper.
Alternatively, you could extract the info directly from the kernel
by performing exactly the same steps that your utility program (ipfw...)
does, but it's overkill for such a simple app.
ipfw show takes up to 0.1s and 500kb to run on my system. Which
is great for manual checks, but almost unacceptable for continuous
monitoring on a server under heavy load. I guess I'll have to learn
how to look up the counters in the kernel.
Thanks anyway!
Best wishes,
Andrew P.
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