Provided by: manpages-dev_2.17-1_all
getgroups, setgroups - get/set list of supplementary group IDs
int getgroups(int size, gid_t list);
int setgroups(size_t size, const gid_t *list);
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.
Sets the supplementary group IDs for the process. Appropriate
privileges (Linux: the CAP_SETGID capability) are required.
On success, the number of supplementary group IDs is returned.
On error, -1 is returned, and errno is set appropriately.
On success, zero is returned. On error, -1 is returned, and
errno is set appropriately.
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
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):
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).
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.
getgid(2), setgid(2), initgroups(3), capabilities(7)