From owner-freebsd-arch  Tue Jan 16 15: 9:45 2001
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To: Poul-Henning Kamp <phk@critter.freebsd.dk>
Subject: Re: dynamic vs static sysctls? 
Cc: Alfred Perlstein <bright@wintelcom.net>, arch@FreeBSD.ORG
In-Reply-To: Your message of "Tue, 16 Jan 2001 08:11:50 +0100."
             <43114.979629110@critter> 
Date: Tue, 16 Jan 2001 15:06:18 -0800
From: Kirk McKusick <mckusick@mckusick.com>
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	To: Kirk McKusick <mckusick@mckusick.com>
	Subject: Re: dynamic vs static sysctls? 
	In-Reply-To: Your message of "Mon, 15 Jan 2001 15:45:35 PST."
		     <200101152345.PAA22257@beastie.mckusick.com> 
	Date: Tue, 16 Jan 2001 08:11:50 +0100
	From: Poul-Henning Kamp <phk@critter.freebsd.dk>

	>I want
	>to do one call to sysctlnametomib (a new, but obviously trivial
	>function) to return the numeric mib, and then use that mib on all
	>the subsequent sysctl calls. 

	As new-sysctl "designer" I think this is a good idea.  It's a trivial
	thing to implement, so are there any warm and able bodies who want 
	to try their hands at it and send the patch to me for review ?

	--
	Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
	phk@FreeBSD.ORG         | TCP/IP since RFC 956
	FreeBSD committer       | BSD since 4.3-tahoe    

Here is my proposal (along with a test program for it).

	Kirk

=-=-=-=-=-=-=-=-=

#include <sys/types.h>
#include <sys/sysctl.h>

int	sysctlnametomib __P((char *name, int *oidp, size_t *sizep));

/*
 * This function uses a presently undocumented interface to the kernel
 * to walk the tree and get the type so it can print the value.
 * This interface is under work and consideration, and should probably
 * be killed with a big axe by the first person who can find the time.
 * (be aware though, that the proper interface isn't as obvious as it
 * may seem, there are various conflicting requirements.
 */
int
sysctlnametomib(char *name, int *oidp, size_t *sizep)
{
	int oid[2];
	int error;

	oid[0] = 0;
	oid[1] = 3;

	*sizep *= sizeof (int);
	error = sysctl(oid, 2, oidp, sizep, name, strlen(name));
	*sizep /= sizeof (int);
	if (error < 0) 
		return (error);
	return (0);
}

/*
 * Test program for sysctlnametomib.
 *
 * Usage: sysctlnametomib name
 */
main(ac, av)
	int ac;
	char *av[];
{
	int i, mib[CTL_MAXNAME];
	size_t size;

	if (ac < 2) {
		printf("Usage: %s name\n", av[0]);
		exit(1);
	}
	size = CTL_MAXNAME;
	if (sysctlnametomib(av[1], mib, &size) < 0) {
		perror("sysctlnametomib");
		exit(1);
	}
	for (i = 0; i < size; i++)
		printf("mib[%d] = %d\n", i, mib[i]);
	exit(0);
}


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