x/sys/unix: Sysctl doesn't supporting writing values

[songgao]

Hello,

This is not really reporting defects but more like a feature request.

In syscall package, or go.sys package, Sysctl is defined as: 

func Sysctl(name string) (value string, err error)

It provides a way to read values through sysctl, but makes it impossible to write/update
values. Internally, it uses "sysctl" defined in each particular OS / ARCH. For
example, (from zsyscall_freebsd_amd64.go):

func sysctl(mib []_C_int, old *byte, oldlen *uintptr, new *byte, newlen uintptr) (err
error)

It would be nice if it can be exported in some way because this is essentially the same
interface as defined in BSD systems. e.g. https://www.freebsd.org/cgi/man.cgi?sysctl(3)

int sysctl(const int *name, u_int namelen, void *oldp, size_t *oldlenp, const void
*newp, size_t newlen);
int sysctlbyname(const char *name, void *oldp, size_t *oldlenp, const void *newp, size_t
newlen);

Can we provide a similar set of functions in go.sys that provides full sysctl support
(both read / write)? If go.sys is not frozen yet, maybe it's a good idea to use the
function names used in most BSD systems, in which case current Sysctl will need to be
renamed to, e.g., SysctlRead.

[ianlancetaylor]

Comment 1:

Labels changed: added repo-sys, release-none.

Status changed to Accepted.

[songgao]

Comment 2:

I'd like to at that, current form of Sysctl only supports string values. If a sysctl
value is integer (e.g. machdep.tsc_freq) , it would be interpreted (not parsed) as
string.

[songgao]

Kudos to the migrating robots :D

I wonder if this issue is best to be in golang/sys now?

[ianlancetaylor]

Yes, this is for the sys subrepo. As Andrew said in his e-mail to golang-dev, we are using this single issue tracker for the subrepos as well.

[songgao]

Got it. Thanks @ianlancetaylor