Function getgrouplist 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn getgrouplist(
    user: *const c_char,
    group: gid_t,
    groups: *mut gid_t,
    ngroups: *mut c_int,
) -> c_int

MT-Safe locale Non-POSIX, see https://www.man7.org/linux/man-pages/man3/getgrouplist.3.html.

Get a list of groups to which a user belongs.