=over =item shmctl ID,CMD,ARG X 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, then ARG must be a variable that will hold the returned C structure. Returns like ioctl: L|/undef EXPR> for error; "C<0> but true" for zero; and the actual return value otherwise. See also L and the documentation for L|IPC::SysV>. Portability issues: L. =back