source: vendor/FreeBSD-libc/current/gen/sysctlbyname.c

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <phk@FreeBSD.org> wrote this file.  As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
 * ----------------------------------------------------------------------------
 *
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/lib/libc/gen/sysctlbyname.c,v 1.5 2002/02/01 00:57:29 obrien Exp $");

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

int
sysctlbyname(const char *name, void *oldp, size_t *oldlenp, void *newp,
             size_t newlen)
{
        int name2oid_oid[2];
        int real_oid[CTL_MAXNAME+2];
        int error;
        size_t oidlen;

        name2oid_oid[0] = 0;    /* This is magic & undocumented! */
        name2oid_oid[1] = 3;

        oidlen = sizeof(real_oid);
        error = sysctl(name2oid_oid, 2, real_oid, &oidlen, (void *)name,
                       strlen(name));
        if (error < 0) 
                return error;
        oidlen /= sizeof (int);
        error = sysctl(real_oid, oidlen, oldp, oldlenp, newp, newlen);
        return (error);
}