osx man page for setgroups

SETGROUPS(2)						      BSD System Calls Manual						      SETGROUPS(2)

NAME
     setgroups -- set group access list

SYNOPSIS
     #include <sys/param.h>
     #include <unistd.h>

     int
     setgroups(int ngroups, const gid_t *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_MAX}.

     Only the super-user may set new groups.

     Use of setgroups() is highly discouraged.

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

ERRORS
     The setgroups() call will fail if:

     [EINVAL]		The value of ngroups is greater than {NGROUPS_MAX}.

     [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(3)

HISTORY
     The setgroups() function call appeared in 4.2BSD.

4.2 Berkeley Distribution					September 15, 2010					 4.2 Berkeley Distribution