1.\"- 2.\" SPDX-License-Identifier: BSD-3-Clause 3.\" 4.\" Copyright (c) 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" Copyright (c) 2025 The FreeBSD Foundation 7.\" 8.\" Portions of this documentation were written by Olivier Certner 9.\" <olce@FreeBSD.org> at Kumacom SARL under sponsorship from the FreeBSD 10.\" Foundation. 11.\" 12.\" Redistribution and use in source and binary forms, with or without 13.\" modification, are permitted provided that the following conditions 14.\" are met: 15.\" 1. Redistributions of source code must retain the above copyright 16.\" notice, this list of conditions and the following disclaimer. 17.\" 2. Redistributions in binary form must reproduce the above copyright 18.\" notice, this list of conditions and the following disclaimer in the 19.\" documentation and/or other materials provided with the distribution. 20.\" 3. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.Dd August 29, 2025 37.Dt GETGROUPLIST 3 38.Os 39.Sh NAME 40.Nm getgrouplist 41.Nd produce a user's effective group list 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In unistd.h 46.Ft int 47.Fn getgrouplist "const char *name" "gid_t basegid" "gid_t *groups" "int *ngroups" 48.Sh DESCRIPTION 49The 50.Fn getgrouplist 51function reads through the group database to retrieve the supplementary groups 52for the user specified in 53.Fa name , 54and returns the effective group list, whose first group is the value of 55.Fa basegid 56and the others are the retrieved supplementary groups. 57.Fa basegid 58typically is the user's group number from the password database. 59.Pp 60The effective group list is returned in the array pointed to by 61.Fa groups . 62The caller specifies the size of the 63.Fa groups 64array in the integer pointed to by 65.Fa ngroups ; 66the actual number of groups found is returned in 67.Fa ngroups . 68.Sh RETURN VALUES 69The 70.Fn getgrouplist 71function 72returns 0 on success and \-1 if the size of the group list is too small to 73hold all the user's groups. 74Here, the group array will be filled with as many groups as will fit. 75.Sh FILES 76.Bl -tag -width /etc/group -compact 77.It Pa /etc/group 78group membership list 79.El 80.Sh SEE ALSO 81.Xr setcred 2 , 82.Xr setgroups 2 , 83.Xr initgroups 3 84.Sh HISTORY 85The 86.Fn getgrouplist 87function first appeared in 88.Bx 4.4 . 89