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.\" 30.Dd January 19, 2018 31.Dt SETGROUPS 2 32.Os 33.Sh NAME 34.Nm setgroups 35.Nd set group access list 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In sys/param.h 40.In unistd.h 41.Ft int 42.Fn setgroups "int ngroups" "const gid_t *gidset" 43.Sh DESCRIPTION 44The 45.Fn setgroups 46system call 47sets the group access list of the current user process 48according to the array 49.Fa gidset . 50The 51.Fa ngroups 52argument 53indicates the number of entries in the array and must be no 54more than 55.Dv {NGROUPS_MAX}+1 . 56.Pp 57Only the super-user may set a new group list. 58.Pp 59The first entry of the group array 60.Pq Va gidset[0] 61is used as the effective group-ID for the process. 62This entry is over-written when a setgid program is run. 63To avoid losing access to the privileges of the 64.Va gidset[0] 65entry, it should be duplicated later in the group array. 66By convention, 67this happens because the group value indicated 68in the password file also appears in 69.Pa /etc/group . 70The group value in the password file is placed in 71.Va gidset[0] 72and that value then gets added a second time when the 73.Pa /etc/group 74file is scanned to create the group set. 75.Sh RETURN VALUES 76.Rv -std setgroups 77.Sh ERRORS 78The 79.Fn setgroups 80system call will fail if: 81.Bl -tag -width Er 82.It Bq Er EPERM 83The caller is not the super-user. 84.It Bq Er EINVAL 85The number specified in the 86.Fa ngroups 87argument is larger than the 88.Dv {NGROUPS_MAX}+1 89limit. 90.It Bq Er EFAULT 91The address specified for 92.Fa gidset 93is outside the process 94address space. 95.El 96.Sh SEE ALSO 97.Xr getgroups 2 , 98.Xr initgroups 3 99.Sh HISTORY 100The 101.Fn setgroups 102system call appeared in 103.Bx 4.2 . 104