=over

=item shmctl ID,CMD,ARG
X<shmctl>

Calls the System V IPC function shmctl.  You'll probably have to say

    use IPC::SysV;

first to get the correct constant definitions.  If CMD is C<IPC_STAT>,
then ARG must be a variable that will hold the returned C<shmid_ds>
structure.  Returns like ioctl: C<undef> for error; "C<0> but
true" for zero; and the actual return value otherwise.
See also L<perlipc/"SysV IPC"> and C<IPC::SysV> documentation.

Portability issues: L<perlport/shmctl>.

=back