setgid — set group identity
#include <sys/types.h> #include <unistd.h>
int
setgid( |
gid_t gid); |
setgid() sets the effective
group ID of the calling process. If the caller is privileged
(has the CAP_SETGID capability), the real GID and saved
set-group-ID are also set.
Under Linux, setgid() is
implemented like the POSIX version with the _POSIX_SAVED_IDS feature. This allows a
set-group-ID program that is not set-user-ID-root to drop all
of its group privileges, do some un-privileged work, and then
reengage the original effective group ID in a secure
manner.
On success, zero is returned. On error, −1 is
returned, and errno is set
appropriately.
The group ID specified in gid is not valid in this
user namespace.
The calling process is not privileged (does not have
the CAP_SETGID
capability), and gid does not match the
real group ID or saved set-group-ID of the calling
process.
The original Linux setgid()
system call supported only 16-bit group IDs. Subsequently,
Linux 2.4 added setgid32()
supporting 32-bit IDs. The glibc setgid() wrapper function transparently
deals with the variation across kernel versions.
At the kernel level, user IDs and group IDs are a
per-thread attribute. However, POSIX requires that all
threads in a process share the same credentials. The NPTL
threading implementation handles the POSIX requirements by
providing wrapper functions for the various system calls
that change process UIDs and GIDs. These wrapper functions
(including the one for setgid()) employ a signal-based technique
to ensure that when one thread changes credentials, all of
the other threads in the process also change their
credentials. For details, see nptl(7).
This page is part of release 4.07 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (C), 1994, Graeme W. Wilford. (Wilf.) and Copyright (C) 2010, 2015, Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Fri Jul 29th 12:56:44 BST 1994 Wilf. <G.Wilfordee.surrey.ac.uk> Modified 1997-01-31 by Eric S. Raymond <esrthyrsus.com> Modified 2002-03-09 by aeb |