bsd man page for setgroups

SETGROUPS(2)							System Calls Manual						      SETGROUPS(2)

NAME
       setgroups - set group access list

SYNOPSIS
       #include <sys/param.h>

       setgroups(ngroups, gidset)
       int ngroups, *gidset;

DESCRIPTION
       Setgroups sets the group access list of the current user process according to the array gidset.	The parameter ngroups indicates the number
       of entries in the array and must be no more than NGROUPS, as defined in <sys/param.h>.

       Only the super-user may set new groups.

RETURN VALUE
       A 0 value is returned on success, -1 on error, with a error code stored in errno.

ERRORS
       The setgroups call will fail if:

       [EPERM]	      The caller is not the super-user.

       [EFAULT]       The address specified for gidset is outside the process address space.

SEE ALSO
       getgroups(2), initgroups(3X)

BUGS
       The gidset array should be of type gid_t, but remains integer for compatibility with earlier systems.

4.2 Berkeley Distribution					   May 13, 1986 						      SETGROUPS(2)