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.Dd January 19, 2018 29.Dt SETGROUPS 2 30.Os 31.Sh NAME 32.Nm setgroups 33.Nd set group access list 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In sys/param.h 38.In unistd.h 39.Ft int 40.Fn setgroups "int ngroups" "const gid_t *gidset" 41.Sh DESCRIPTION 42The 43.Fn setgroups 44system call 45sets the group access list of the current user process 46according to the array 47.Fa gidset . 48The 49.Fa ngroups 50argument 51indicates the number of entries in the array and must be no 52more than 53.Dv {NGROUPS_MAX}+1 . 54.Pp 55Only the super-user may set a new group list. 56.Pp 57The first entry of the group array 58.Pq Va gidset[0] 59is used as the effective group-ID for the process. 60This entry is over-written when a setgid program is run. 61To avoid losing access to the privileges of the 62.Va gidset[0] 63entry, it should be duplicated later in the group array. 64By convention, 65this happens because the group value indicated 66in the password file also appears in 67.Pa /etc/group . 68The group value in the password file is placed in 69.Va gidset[0] 70and that value then gets added a second time when the 71.Pa /etc/group 72file is scanned to create the group set. 73.Sh RETURN VALUES 74.Rv -std setgroups 75.Sh ERRORS 76The 77.Fn setgroups 78system call will fail if: 79.Bl -tag -width Er 80.It Bq Er EPERM 81The caller is not the super-user. 82.It Bq Er EINVAL 83The number specified in the 84.Fa ngroups 85argument is larger than the 86.Dv {NGROUPS_MAX}+1 87limit. 88.It Bq Er EFAULT 89The address specified for 90.Fa gidset 91is outside the process 92address space. 93.El 94.Sh SEE ALSO 95.Xr getgroups 2 , 96.Xr initgroups 3 97.Sh HISTORY 98The 99.Fn setgroups 100system call appeared in 101.Bx 4.2 . 102