Name
getgroups, setgroups — get/set list of supplementary group IDs
Synopsis
#include <sys/types.h> #include <unistd.h>
int getgroups( |
int size, |
gid_t list[]); |
#include <grp.h>
int setgroups( |
size_t size, |
const gid_t *list); |
![[Note]](../stylesheet/note.png) |
Note | ||
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DESCRIPTION
getgroups() returns the
supplementary group IDs of the calling process in list. The argument size should be set to the
maximum number of items that can be stored in the buffer
pointed to by list.
If the calling process is a member of more than size supplementary groups, then
an error results. It is unspecified whether the effective
group ID of the calling process is included in the returned
list. (Thus, an application should also call getegid(2) and add or
remove the resulting value.)
If size is zero,
list is not modified,
but the total number of supplementary group IDs for the
process is returned. This allows the caller to determine the
size of a dynamically allocated list to be used in a further
call to getgroups().
setgroups() sets the
supplementary group IDs for the calling process. Appropriate
privileges (Linux: the CAP_SETGID capability) are required. The
size argument
specifies the number of supplementary group IDs in the buffer
pointed to by list.
RETURN VALUE
On success, getgroups()
returns the number of supplementary group IDs. On error,
−1 is returned, and errno
is set appropriately.
On success, setgroups()
returns 0. On error, −1 is returned, and errno is set appropriately.
ERRORS
- EFAULT
-
listhas an invalid address.
getgroups() can additionally
fail with the following error:
- EINVAL
-
sizeis less than the number of supplementary group IDs, but is not zero.
setgroups() can additionally
fail with the following errors:
- EINVAL
-
sizeis greater thanNGROUPS_MAX(32 before Linux 2.6.4; 65536 since Linux 2.6.4). - ENOMEM
-
Out of memory.
- EPERM
-
The calling process has insufficient privilege.
CONFORMING TO
SVr4, 4.3BSD. The getgroups() function is in POSIX.1-2001.
Since setgroups() requires
privilege, it is not covered by POSIX.1-2001.
NOTES
A process can have up to NGROUPS_MAX supplementary group IDs in
addition to the effective group ID. The set of supplementary
group IDs is inherited from the parent process, and preserved
across an execve(2).
The maximum number of supplementary group IDs can be found using sysconf(3):
long ngroups_max;
ngroups_max = sysconf(_SC_NGROUPS_MAX);
The maximum return value of getgroups() cannot be larger than one more
than this value.
COLOPHON
This page is part of release 3.24 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
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Copyright 1993 Rickard E. Faith (faithcs.unc.edu) 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. Modified Thu Oct 31 12:04:29 1996 by Eric S. Raymond <esrthyrsus.com> Modified, 27 May 2004, Michael Kerrisk <mtk.manpagesgmail.com> Added notes on capability requirements 2008-05-03, mtk, expanded and rewrote parts of DESCRIPTION and RETURN VALUE, made style of page more consistent with man-pages style. |