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system callers of getgroups(), getgrouplist(), and setgroups() to
allocate buffers dynamically. Specifically, allocate a buffer of size
sysconf(_SC_NGROUPS_MAX)+1 (+2 in a few cases to allow for overflow).
This (or similar gymnastics) is required for the code to actually follow
the POSIX.1-2008 specification where {NGROUPS_MAX} may differ at runtime
and where getgroups may return {NGROUPS_MAX}+1 results on systems like
FreeBSD which include the primary group.
In id(1), don't pointlessly add the primary group to the list of all
groups, it is always the first result from getgroups(). In principle
the old code was more portable, but this was only done in one of the two
places where getgroups() was called to the overall effect was pointless.
Document the actual POSIX requirements in the getgroups(2) and
setgroups(2) manpages. We do not yet support a dynamic NGROUPS, but we
may in the future.
MFC after: 2 weeks
102 lines
3.0 KiB
Groff
102 lines
3.0 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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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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.\" 4. 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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.\" @(#)getgroups.2 8.2 (Berkeley) 4/16/94
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.\" $FreeBSD$
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.\"
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.Dd March 5, 1999
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.Dt GETGROUPS 2
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.Os
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.Sh NAME
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.Nm getgroups
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.Nd get 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/types.h
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.In unistd.h
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.Ft int
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.Fn getgroups "int gidsetlen" "gid_t *gidset"
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.Sh DESCRIPTION
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The
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.Fn getgroups
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system call
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gets the current group access list of the user process
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and stores it in the array
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.Fa gidset .
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The
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.Fa gidsetlen
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argument
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indicates the number of entries that may be placed in
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.Fa gidset .
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The
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.Fn getgroups
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system call
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returns the actual number of groups returned in
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.Fa gidset .
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At least one and as many as {NGROUPS_MAX}+1 values may be returned.
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If
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.Fa gidsetlen
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is zero,
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.Fn getgroups
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returns the number of supplementary group IDs associated with
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the calling process without modifying the array pointed to by
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.Fa gidset .
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.Sh RETURN VALUES
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A successful call returns the number of groups in the group set.
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A value of -1 indicates that an error occurred, and the error
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code is stored in the global variable
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.Va errno .
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.Sh ERRORS
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The possible errors for
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.Fn getgroups
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are:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The argument
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.Fa gidsetlen
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is smaller than the number of groups in the group set.
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.It Bq Er EFAULT
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The argument
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.Fa gidset
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specifies
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an invalid address.
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.El
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.Sh SEE ALSO
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.Xr setgroups 2 ,
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.Xr initgroups 3
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.Sh STANDARDS
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The
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.Fn getgroups
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system call conforms to
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.St -p1003.1-2008 .
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.Sh HISTORY
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The
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.Fn getgroups
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system call appeared in
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.Bx 4.2 .
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