1.\" Copyright (c) 1983, 1991, 1993, 1994 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)setgroups.2 8.2 (Berkeley) 4/16/94 29.\" $FreeBSD$ 30.\" 31.Dd January 19, 2018 32.Dt SETGROUPS 2 33.Os 34.Sh NAME 35.Nm setgroups 36.Nd set group access list 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In sys/param.h 41.In unistd.h 42.Ft int 43.Fn setgroups "int ngroups" "const gid_t *gidset" 44.Sh DESCRIPTION 45The 46.Fn setgroups 47system call 48sets the group access list of the current user process 49according to the array 50.Fa gidset . 51The 52.Fa ngroups 53argument 54indicates the number of entries in the array and must be no 55more than 56.Dv {NGROUPS_MAX}+1 . 57.Pp 58Only the super-user may set a new group list. 59.Pp 60The first entry of the group array 61.Pq Va gidset[0] 62is used as the effective group-ID for the process. 63This entry is over-written when a setgid program is run. 64To avoid losing access to the privileges of the 65.Va gidset[0] 66entry, it should be duplicated later in the group array. 67By convention, 68this happens because the group value indicated 69in the password file also appears in 70.Pa /etc/group . 71The group value in the password file is placed in 72.Va gidset[0] 73and that value then gets added a second time when the 74.Pa /etc/group 75file is scanned to create the group set. 76.Sh RETURN VALUES 77.Rv -std setgroups 78.Sh ERRORS 79The 80.Fn setgroups 81system call will fail if: 82.Bl -tag -width Er 83.It Bq Er EPERM 84The caller is not the super-user. 85.It Bq Er EINVAL 86The number specified in the 87.Fa ngroups 88argument is larger than the 89.Dv {NGROUPS_MAX}+1 90limit. 91.It Bq Er EFAULT 92The address specified for 93.Fa gidset 94is outside the process 95address space. 96.El 97.Sh SEE ALSO 98.Xr getgroups 2 , 99.Xr initgroups 3 100.Sh HISTORY 101The 102.Fn setgroups 103system call appeared in 104.Bx 4.2 . 105