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

NAME
     initgroups -- initialize group access list

LIBRARY
     Standard system libraries.

SYNOPSIS
     #include <unistd.h>

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

DESCRIPTION
     The initgroups() function calculates a group access list for the user
     specified in name.  This group list is then saved in the kernel creden-
     tials for the current process.  The basegid is included in the groups
     list.  Typically this value is given as the default group associated with
     the user's account record.

     This function sets at most 16 group IDs in the process credentials.  This
     list can be retrieved using the getgroups(2) function.  Note that OS X
     supports group membership in an unlimited number of groups.  The OS X
     kernel uses the group list stored in the process credentials only as an
     initial cache.  Additional group memberships are determined by communica-
     tion between the operating system and the opendirectoryd daemon.

     Processes should not use the group ID numbers from getgroups(2) to deter-
     mine a user's group membership.  The list obtained from getgroups() may
     only be a partial list of a user's group membership.  Membership checks
     should use the mbr_gid_to_uuid(3), mbr_uid_to_uuid(3), and
     mbr_check_membership(3) functions.

RETURN VALUES
     The initgroups() function returns 0 on success.  On failure, this func-
     tion will return -1 and set errno to one of the following values:

     [EPERM]   The caller's effictive UID is not zero.

     [EINVAL]  Internal error, an invalid array size was supplied to the ker-
               nel.

     [EFAULT]  Internal error, invalid data was supplied to the kernel.

SEE ALSO
     getgroups(2), getgrouplist(3), mbr_gid_to_uuid(3), mbr_uid_to_uuid(3),
     mbr_check_membership(3).

HISTORY
     The initgroups() function appeared in 4.2BSD.

BSD                              June 4, 1993                              BSD