GETGROUPS

NAME

SYNOPSIS

int getgroups(int size, gid_t list[]);

#include <grp.h>

int setgroups(size_t size, const gid_t *list);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

setgroups(): _BSD_SOURCE  

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, setgroups() returns 0. On error, -1 is returned, and errno is set appropriately.  

ERRORS

EFAULT

list has an invalid address.

getgroups() can additionally fail with the following error:

EINVAL

size is less than the number of supplementary group IDs, but is not zero.

setgroups() can additionally fail with the following errors:

EINVAL

size is greater than NGROUPS_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

NOTES

The maximum number of supplementary group IDs can be found using sysconf(3):

    long ngroups_max;
    ngroups_max = sysconf(_SC_NGROUPS_MAX);

SEE ALSO

COLOPHON