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.\" Copyright (C), 1994, Graeme W. Wilford. (Wilf.)
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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.\" manual page may be incorrect or out-of-date.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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.\" Fri Jul 29th 12:56:44 BST 1994 Wilf. <G.Wilford@ee.surrey.ac.uk>
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.\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
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.\" Modified 2002-03-09 by aeb
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.\"
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2009-10-17 04:36:12 +00:00
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.TH SETGID 2 2009-10-17 "Linux" "Linux Programmer's Manual"
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.SH NAME
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setgid \- set group identity
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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 setgid(gid_t " gid );
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.SH DESCRIPTION
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.BR setgid ()
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sets the effective group ID of the calling process.
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If the caller is the
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superuser, the real GID and saved set-group-ID are also set.
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Under Linux,
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.BR setgid ()
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is implemented like the POSIX version with the
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.B _POSIX_SAVED_IDS
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feature.
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This allows a set-group-ID program that is not set-user-ID-root
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to drop all of its group
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privileges, do some un-privileged work, and then re-engage the original
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effective group ID in a secure manner.
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.SH "RETURN VALUE"
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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 EPERM
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The calling process is not privileged (does not have the
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\fBCAP_SETGID\fP capability), and
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.I gid
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does not match the real group ID or saved set-group-ID of
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the calling process.
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.SH "CONFORMING TO"
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SVr4, POSIX.1-2001.
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.SH "SEE ALSO"
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.BR getgid (2),
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.BR setegid (2),
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.BR setregid (2),
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.BR capabilities (7),
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.BR credentials (7)
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