.\"
.\" Copyright (c) 2008-2011 Apple Inc. All rights reserved.
.\"
.\" @APPLE_LICENSE_HEADER_START@
.\"
.\" This file contains Original Code and/or Modifications of Original Code
.\" as defined in and that are subject to the Apple Public Source License
.\" Version 2.0 (the 'License'). You may not use this file except in
.\" compliance with the License. Please obtain a copy of the License at
.\" http://www.opensource.apple.com/apsl/ and read it before using this
.\" file.
.\"
.\" The Original Code and all software distributed under the License are
.\" distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
.\" EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
.\" INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
.\" FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
.\" Please see the License for the specific language governing rights and
.\" limitations under the License.
.\"
.\" @APPLE_LICENSE_HEADER_END@
.\"
.\"
.\" $NetBSD: getgroups.2,v 1.8 1995/02/27 12:32:57 cgd Exp $
.\"
.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)getgroups.2 8.2 (Berkeley) 4/16/94
.\"
.Dd October 28, 2011
.Dt GETGROUPS 2
.Os BSD 4.2
.Sh NAME
.Nm getgroups
.Nd get group access list
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fo getgroups
.Fa "int gidsetsize"
.Fa "gid_t grouplist[]"
.Fc
.Sh DESCRIPTION
.Fn getgroups
gets the current group access list of the current user process
and stores it in the array
.Fa grouplist[] .
The parameter
.Fa gidsetsize
indicates the number of entries that may be placed in
.Fa grouplist[] .
.Fn getgroups
returns the actual number of groups returned in
.Fa grouplist[] .
However, no more than
.Dv {NGROUPS_MAX}
will be returned. If
.Fa gidsetsize
is 0,
.Fn getgroups
returns the number of groups without modifying the
.Fa grouplist[]
array.
.Pp
Calling
.Xr initgroups 3
to opt-in for supplementary groups will cause
.Fn getgroups
to return a single entry, the GID that was passed to
.Xr initgroups 3 .
.Pp
To provide compatibility with applications that use
.Fn getgroups
in environments where users may be in more than
.Dv {NGROUPS_MAX}
groups, a variant of
.Fn getgroups ,
obtained when compiling with either the macros
.Dv _DARWIN_UNLIMITED_GETGROUPS
or
.Dv _DARWIN_C_SOURCE
defined, can be used that is not limited to
.Dv {NGROUPS_MAX}
groups.
However, this variant only returns the user's default group access list and
not the group list modified by a call to
.Xr setgroups 2
(either in the current process or an ancestor process).
Use of
.Xr setgroups 2
is highly discouraged, and there is no foolproof way to determine if it has
been previously called.
.Sh RETURN VALUES
A successful call returns the number of groups in the group set.
Otherwise, a value of -1 is returned and the global integer variable
.Va errno
is set to indicate the error.
.Sh ERRORS
The possible errors for
.Fn getgroups
are:
.Bl -tag -width Er
.\" ==========
.It Bq Er EFAULT
The argument
.Fa grouplist
specifies an invalid address.
.\" ==========
.It Bq Er EINVAL
The argument
.Fa gidsetsize ,
although non-zero,
is smaller than the number of groups in the group set.
.El
.Sh LEGACY SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/types.h>
.Fd #include <unistd.h>
.Pp
The include files
.In sys/param.h
and
.In sys/types.h
are necessary.
.Sh SEE ALSO
.Xr setgroups 2 ,
.Xr initgroups 3 ,
.Xr compat 5
.Sh HISTORY
The
.Fn getgroups
function call appeared in
.Bx 4.2 .