GETGROUPS
Section: Linux Programmer's Manual (2)
Updated: 2004-05-27
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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);
DESCRIPTION
- getgroups
-
Up to
size
supplementary group IDs (of the calling process) are returned in
list.
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.
- setgroups
-
Sets the supplementary group IDs for the process.
Appropriate privileges (Linux: the
CAP_SETGID
capability) are required.
RETURN VALUE
- getgroups
-
On success, the number of supplementary group IDs is returned.
On error, -1 is returned, and
errno
is set appropriately.
- setgroups
-
On success, zero is returned. On error, -1 is returned, and
errno
is set appropriately.
ERRORS
- EFAULT
-
list
has an invalid address.
- EINVAL
-
For
setgroups,
size
is greater than
NGROUPS
(32 for Linux 2.0.32).
For
getgroups,
size
is less than the number of supplementary group IDs, but is not zero.
- EPERM
-
The calling process has insufficient privilege to call
setgroups.
NOTES
A process can have up to at least 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 may be changed using
setgroups.
The maximum number of supplementary group IDs can be found using
sysconf(3):
long ngroups_max;
ngroups_max = sysconf(_SC_NGROUPS_MAX);
The maximal return value of
getgroups
cannot be larger than one more than the value obtained this way.
The prototype for
setgroups
is only available if
_BSD_SOURCE
is defined (either explicitly, or implicitly, by not defining
_POSIX_SOURCE or compiling with the -ansi flag).
CONFORMING TO
SVr4, SVID (issue 4 only; these calls were not present in SVr3),
X/OPEN, 4.3BSD. The
getgroups
function is in POSIX.1. Since
setgroups
requires privilege, it is not covered by POSIX.1.
SEE ALSO
getgid(2),
setgid(2),
initgroups(3),
capabilities(7)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- NOTES
-
- CONFORMING TO
-
- SEE ALSO
-
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