osx man page for getgrouplist

GETGROUPLIST(3) 					   BSD Library Functions Manual 					   GETGROUPLIST(3)

NAME
     getgrouplist -- calculate group access list

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <unistd.h>

     int
     getgrouplist(const char *name, int basegid, int *groups, int *ngroups);

DESCRIPTION
     The getgrouplist() function reads through the group file and calculates the group access list for the user specified in name.  The basegid is
     automatically included in the groups list.  Typically this value is given as the group number from the password file.

     The resulting group list is returned in the array pointed to by groups.  The caller specifies the size of the groups array in the integer
     pointed to by ngroups; the actual number of groups found is returned in ngroups.

RETURN VALUES
     The getgrouplist() function returns -1 if the size of the group list is too small to hold all the user's groups.  Here, the group array will
     be filled with as many groups as will fit.

FILES
     /etc/group  group membership list

SEE ALSO
     setgroups(2), initgroups(3)

HISTORY
     The getgrouplist() function first appeared in 4.4BSD.

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

BSD
								   June 9, 1993 							       BSD