_SC_NGROUPS_MAX
int ng = (int)sysconf(_SC_NGROUPS_MAX);
case _SC_NGROUPS_MAX:
{ "NGROUPS_MAX", SYSCONF, _SC_NGROUPS_MAX },
maxgroups = sysconf(_SC_NGROUPS_MAX);
*ngroupsmax = (int)sysconf(_SC_NGROUPS_MAX);