mirror of https://github.com/mkerrisk/man-pages
133 lines
3.7 KiB
Groff
133 lines
3.7 KiB
Groff
.\" Hey Emacs! This file is -*- nroff -*- source.
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.\"
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.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.\" Modified Thu Oct 31 12:04:29 1996 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified, 27 May 2004, Michael Kerrisk <mtk-manpages@gmx.net>
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.\" Added notes on capability requirements
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.\"
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.TH GETGROUPS 2 2004-05-27 "Linux 2.6.6" "Linux Programmer's Manual"
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.SH NAME
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getgroups, setgroups \- get/set list of supplementary group IDs
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.SH SYNOPSIS
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.B #include <sys/types.h>
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.br
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.B #include <unistd.h>
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.sp
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.BI "int getgroups(int " size ", gid_t " list []);
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.sp
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.B #include <grp.h>
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.sp
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.BI "int setgroups(size_t " size ", const gid_t *" list );
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.SH DESCRIPTION
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.TP
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.BR getgroups ()
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Up to
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.I size
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supplementary group IDs (of the calling process) are returned in
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.IR list .
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It is unspecified whether the effective group ID of the calling process
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is included in the returned list.
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(Thus, an application should also call
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.BR getegid (2)
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and add or remove the resulting value.)
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If
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.I size
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is zero,
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.I list
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is not modified, but the total number of supplementary group IDs for the
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process is returned.
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.TP
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.BR setgroups ()
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Sets the supplementary group IDs for the process.
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Appropriate privileges (Linux: the
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.B CAP_SETGID
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capability) are required.
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.SH "RETURN VALUE"
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.TP
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.BR getgroups ()
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On success, the number of supplementary group IDs is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.TP
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.BR setgroups ()
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On success, zero is returned.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP
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.B EFAULT
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.I list
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has an invalid address.
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.TP
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.B EINVAL
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For
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.BR setgroups (),
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.I size
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is greater than
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.B NGROUPS
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(32 for Linux 2.0.32).
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For
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.BR getgroups (),
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.I size
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is less than the number of supplementary group IDs, but is not zero.
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.TP
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.B EPERM
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The calling process has insufficient privilege to call
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.BR setgroups ().
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.SH NOTES
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A process can have up to at least NGROUPS_MAX supplementary group IDs
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in addition to the effective group ID. The set of supplementary group IDs
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is inherited from the parent process and may be changed using
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.BR setgroups ().
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The maximum number of supplementary group IDs can be found using
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.BR sysconf (3):
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.nf
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long ngroups_max;
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ngroups_max = sysconf(_SC_NGROUPS_MAX);
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.fi
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The maximal return value of
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.BR getgroups ()
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cannot be larger than one more than the value obtained this way.
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.LP
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The prototype for
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.BR setgroups ()
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is only available if
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.B _BSD_SOURCE
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is defined.
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.SH "CONFORMING TO"
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SVr4, 4.3BSD.
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The
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.BR getgroups ()
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function is in POSIX.1-2001.
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Since
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.BR setgroups ()
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requires privilege, it is not covered by POSIX.1-2001.
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.SH "SEE ALSO"
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.BR getgid (2),
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.BR setgid (2),
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.BR initgroups (3),
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.BR capabilities (7)
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