Date: Wed, 13 Aug 2014 20:29:21 +0200 From: Lars Engels <lme@freebsd.org> To: "Sam Fourman Jr." <sfourman@gmail.com> Cc: hackers@freebsd.org Subject: Re: sysctl(3) question Message-ID: <20140813182921.GG98029@e-new.0x20.net> In-Reply-To: <CAOFF%2BZ2y3W7d1EL0PcEQCy28i1oOXDTDhW8z4UyfBUiHgkk6Jg@mail.gmail.com> References: <CAOFF%2BZ2y3W7d1EL0PcEQCy28i1oOXDTDhW8z4UyfBUiHgkk6Jg@mail.gmail.com>
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On Wed, Aug 13, 2014 at 12:00:32PM -0500, Sam Fourman Jr. wrote:
> Hello Hackers,
>=20
> the following command gives me the disks in a system
> sysctl kern.disks
> kern.disks: cd0 ada0
>=20
>=20
> my question is, what paramaters and values do I have to pass sysctl(3) to
> give me those disks?
>=20
>=20
>=20
> I have tried and I cant get HW_DISKNAMES from <sys/sysctl.h> to work
>=20
>=20
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/param.h>
> #include <sys/sysctl.h>
> #include <err.h>
>=20
> int main(void) {
>=20
> int mib[2];
> size_t len;
> char *p;
>=20
> mib[0] =3D CTL_HW;
> mib[1] =3D HW_DISKNAMES;
>=20
> /* Determine how much space to allocate. */
> if (sysctl(mib, 2, NULL, &len, NULL, 0) =3D=3D -1)
> err(1, "sysctl");
>=20
> if ((p =3D (char *)malloc(len)) =3D=3D NULL)
> err(1, NULL);
>=20
> /* Populate the allocated area with the string returned
> * * by sysctl.
> * */
> if (sysctl(mib, 2, p, &len, NULL, 0) =3D=3D -1)
> err(1, "sysctl");
>=20
> printf("%s\n", p);
>=20
> return 0;
> }
Try sysctlbyname():
#include <stdio.h>
#include <stdlib.h>
#include <sys/param.h>
#include <sys/sysctl.h>
#include <err.h>
int main(void) {
size_t len;
char *p;
/* Determine how much space to allocate. */
if (sysctlbyname("kern.disks", NULL, &len, NULL, 0) =3D=3D -1)
err(1, "sysctl");
if ((p =3D (char *)malloc(len)) =3D=3D NULL)
err(1, NULL);
if (sysctlbyname("kern.disks", p, &len, NULL, 0) =3D=3D -1)
err(1, "sysctl");
printf("%s\n", p);
return 0;
}
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