setgroups - write group numbers

Syntax	#include <unistd.h> int setgroups(int ngroups, const gid_t grouplist[]);
Description	The setgroups() function can only be called by the system administrator. The setgroups() function sets the group access list of the calling process from the group numbers field. The number of entries is specified by the ngroups parameter and must not exceed NGROUPS_MAX.
Return val.	0 -1	if successful. if unsuccessful. errno indicates the cause of the error.
Errors	setgroups() will fail if:
	EINVAL	The value ngroups exceeds NGROUPS_MAX.
	EFAULT	A referenced part of the grouplist array is outside the address range assigned to the process.
EPERM	The effective user number is not the user number of the system administrator.