105 lines
3.2 KiB
Groff
105 lines
3.2 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993, 1994
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)setgroups.2 8.2 (Berkeley) 4/16/94
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.\" $FreeBSD$
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.\"
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.Dd January 19, 2018
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.Dt SETGROUPS 2
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.Os
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.Sh NAME
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.Nm setgroups
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.Nd set group access list
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/param.h
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.In unistd.h
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.Ft int
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.Fn setgroups "int ngroups" "const gid_t *gidset"
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.Sh DESCRIPTION
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The
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.Fn setgroups
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system call
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sets the group access list of the current user process
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according to the array
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.Fa gidset .
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The
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.Fa ngroups
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argument
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indicates the number of entries in the array and must be no
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more than
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.Dv {NGROUPS_MAX}+1 .
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.Pp
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Only the super-user may set a new group list.
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.Pp
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The first entry of the group array
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.Pq Va gidset[0]
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is used as the effective group-ID for the process.
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This entry is over-written when a setgid program is run.
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To avoid losing access to the privileges of the
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.Va gidset[0]
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entry, it should be duplicated later in the group array.
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By convention,
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this happens because the group value indicated
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in the password file also appears in
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.Pa /etc/group .
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The group value in the password file is placed in
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.Va gidset[0]
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and that value then gets added a second time when the
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.Pa /etc/group
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file is scanned to create the group set.
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.Sh RETURN VALUES
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.Rv -std setgroups
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.Sh ERRORS
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The
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.Fn setgroups
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system call will fail if:
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.Bl -tag -width Er
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.It Bq Er EPERM
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The caller is not the super-user.
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.It Bq Er EINVAL
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The number specified in the
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.Fa ngroups
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argument is larger than the
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.Dv {NGROUPS_MAX}+1
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limit.
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.It Bq Er EFAULT
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The address specified for
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.Fa gidset
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is outside the process
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address space.
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.El
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.Sh SEE ALSO
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.Xr getgroups 2 ,
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.Xr initgroups 3
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.Sh HISTORY
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The
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.Fn setgroups
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system call appeared in
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.Bx 4.2 .
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