SIGNATURE Wait

-- waiting for child processes

IMPORT
  Pair[process,childstat]
                      ONLY pair: SORT
  Option[pair[process,childstat]]
                      ONLY option: SORT
  Com[pair[process,childstat]]
                      ONLY com: SORT
  Com[option[pair[process,childstat]]]
                      ONLY com: SORT
  ProcessCtrl         ONLY process: SORT procstat: SORT
  Signal              ONLY signal: SORT

TYPE childstat == exited   (status: procstat)
                  -- child process terminated normally
                  signalled(signal: signal)
                  -- child process terminated due to a POSIX signal
                  signalledUnknown
                  -- child process terminated due to some non-POSIX signal
                  stopped  (signal: signal)
                  -- child process was stopped due to a POSIX signal
                  stoppedUnknown
                  -- child process was stopped due to some non-POSIX signal

FUN wait    : com[pair[process,childstat]]
              -- wait for any child
    wait    : com[option[pair[process,childstat]]]
              -- as above, but non-blocking
    wait    : process -> com[pair[process,childstat]]
              -- wait for specific process
    wait    : process -> com[option[pair[process,childstat]]]
              -- as above, but non-blocking
    waitGrp : com[pair[process,childstat]]
              -- wait for any child in this process group
    waitGrp : com[option[pair[process,childstat]]]
              -- as above, but non-blocking
    waitGrp : process -> com[pair[process,childstat]]
              -- wait for any child in the specified process group
    waitGrp : process -> com[option[pair[process,childstat]]]
              -- as above, but non-blocking
    -- see POSIX waitpid()
    -- NOTE that the status of stopped children will always be reported.
    -- NOTE that process groups have the same representation as processes.
    --      Such is the nature of operating systems.