opendarwin man page for getgroups

GETGROUPS(2)						      BSD System Calls Manual						      GETGROUPS(2)

NAME
     getgroups -- get group access list

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

     int
     getgroups(int gidsetlen, gid_t *gidset);

DESCRIPTION
     Getgroups() gets the current group access list of the current user process and stores it in the array gidset.  The parameter gidsetlen indi-
     cates the number of entries that may be placed in gidset.	Getgroups() returns the actual number of groups returned in gidset.  No more than
     {NGROUPS_MAX} will ever be returned.  If gidsetlen is 0, getgroups() returns the number of groups without modifying the gidset array.

RETURN VALUES
     A successful call returns the number of groups in the group set.  A value of -1 indicates that an error occurred, and the error code is
     stored in the global variable errno.

ERRORS
     The possible errors for getgroups() are:

     [EINVAL]		The argument gidsetlen is smaller than the number of groups in the group set.

     [EFAULT]		The argument gidset specifies an invalid address.

SEE ALSO
     setgroups(2), initgroups(3)

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

4.2 Berkeley Distribution					  April 16, 1994					 4.2 Berkeley Distribution