osx man page for initgroups

INITGROUPS(3)						   BSD Library Functions Manual 					     INITGROUPS(3)

NAME
     initgroups -- initialize group access list

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     initgroups(const char *name, int basegid);

DESCRIPTION
     The initgroups() function uses the getgrouplist(3) function to calculate the group access list for the user specified in name.  This group
     list is then setup for the current process using setgroups(2).  The basegid is automatically included in the groups list.	Typically this
     value is given as the group number from the password file.

RETURN VALUES
     The initgroups() function returns -1 if it was not invoked by the super-user.

SEE ALSO
     setgroups(2), getgrouplist(3)

HISTORY
     The initgroups() function appeared in 4.2BSD.

BUGS
     The getgrouplist() function called by initgroups() uses the routines based on getgrent(3).  If the invoking program uses any of these rou-
     tines, the group structure will be overwritten in the call to initgroups().

BSD
								   June 4, 1993 							       BSD