The various Exec functions such as doio(), sendio(), abortio() and
checkio() operate normally. the only caveats are that cmd_write may cause
your application to wait internally, even with SendIO(), and a task using
cmd_read to wait on a response from a console is at the user's mercy.  if
the user never reselects that window, and the console response provides
the only wake-up call, that task will sleep forever.