The getgroups() function gets the current supplemental group access list of the calling process and stores the result in the array of group IDs specified by grouplist. This array has gidsetsize entries and must be large enough to contain the entire list. This list cannot be larger than NGROUPS_MAX. If gidsetsize equals 0, getgroups() will return the number of groups to which the calling process belongs without modifying the array pointed to by grouplist.

The setgroups() function sets the supplementary group access list of the calling process from the array of group IDs specified by grouplist. The number of entries is specified by ngroups and can not be greater than NGROUPS_MAX.

Upon successful completion, getgroups() returns the number of supplementary group IDs set for the calling process and setgroups() returns 0. Otherwise, -1 is returned and errno is set to indicate the error.

The getgroups() and setgroups() functions will fail if:

EFAULT

A referenced part of the array pointed to by grouplist is an illegal address.

The getgroups() function will fail if:

EINVAL

The value of gidsetsize is non-zero and less than the number of supplementary group IDs set for the calling process.

The setgroups() function will fail if:

EINVAL

The value of ngroups is greater than NGROUPS_MAX.

EPERM

The effective user of the calling process is not super-user.

Use of the setgroups() function requires superuser privileges.

See attributes(5) for descriptions of the following attributes:

groups(1), chown(2), getuid(2), setuid(2), getgrnam(3C), initgroups(3C), attributes(5)