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Diffstat (limited to 'lib/libsys/getgroups.2')
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diff --git a/lib/libsys/getgroups.2 b/lib/libsys/getgroups.2 new file mode 100644 index 000000000000..4881a65d532e --- /dev/null +++ b/lib/libsys/getgroups.2 @@ -0,0 +1,157 @@ +.\"- +.\" SPDX-License-Identifier: BSD-3-Clause +.\" +.\" Copyright (c) 1983, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" Copyright (c) 2025 The FreeBSD Foundation +.\" +.\" Portions of this documentation were written by Olivier Certner +.\" <olce@FreeBSD.org> at Kumacom SARL under sponsorship from the FreeBSD +.\" Foundation. +.\" +.\" 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. 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. +.\" +.Dd September 17, 2025 +.Dt GETGROUPS 2 +.Os +.Sh NAME +.Nm getgroups +.Nd get the calling process' supplementary groups +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In unistd.h +.Ft int +.Fn getgroups "int gidsetlen" "gid_t *gidset" +.Sh DESCRIPTION +The +.Fn getgroups +system call gets the calling process' supplementary groups and stores them in +the +.Fa gidset +array in strictly ascending order. +The value of +.Fa gidsetlen +indicates the maximum number of entries that may be placed in +.Fa gidset . +.Pp +If +.Fa gidsetlen +is zero, +.Fn getgroups +returns the cardinal of the calling process' supplementary groups set and +ignores argument +.Fa gidset . +.Pp +No more than +.Dv {NGROUPS_MAX} +values may ever be returned. +The value of +.Dv {NGROUPS_MAX} +should be obtained using +.Xr sysconf 3 +to avoid hard-coding it into the executable. +.Sh RETURN VALUES +On success, the +.Fn getgroups +system call returns the cardinal of the supplementary groups set. +It always succeeds if argument +.Fa gidsetlen +is zero. +.Pp +A value of -1 indicates that an error occurred, and the error +code is stored in the global variable +.Va errno . +.Sh ERRORS +The possible errors for +.Fn getgroups +are: +.Bl -tag -width Er +.It Bq Er EINVAL +The argument +.Fa gidsetlen +is smaller than the number of supplementary groups +.Pq but not zero . +.It Bq Er EFAULT +An invalid address was encountered while reading from the +.Fa gidset +array. +.El +.Sh SEE ALSO +.Xr setgroups 2 , +.Xr initgroups 3 , +.Xr sysconf 3 +.Sh STANDARDS +The +.Fn getgroups +system call conforms to +.St -p1003.1-2008 +with the additional properties that supplementary groups are reported in +strictly ascending order and the returned size coincides with the cardinal of +the set. +.Sh HISTORY +The +.Fn getgroups +system call appeared in +.Bx 4.2 . +.Pp +Since +.Fx 14.3 , +the +.Fn getgroups +system call has treated the supplementary groups as a set, reporting them in +strictly ascending order and returning the cardinal of the set. +.Pp +Before +.Fx 15.0 , +the +.Fn getgroups +system call would additionally return the effective group ID as the first +element of the array, before the supplementary groups. +.Sh SECURITY CONSIDERATIONS +The +.Fn getgroups +system call gets the supplementary groups set in the +.Fa gidset +array. +In particular, as evoked in +.Sx HISTORY , +it does not anymore retrieve the effective GID in the first slot of +.Fa gidset . +Programs should not make any assumption about which group is placed in the first +slot of +.Fa gidset +other than it being the supplementary group with smallest GID. +.Pp +The effective GID is present in the supplementary groups set if and only if it +was explicitly set as a supplementary group. +The function +.Fn initgroups +enforces that, while the +.Fn setgroups +system call does not. +Please consult the +.Xr initgroups 3 +manual page for the rationale. |