Manuel M. T. Chakravarty
Fri, 27 Jul 2001 11:44:04 +1000
George Russell <email@example.com> wrote,
> Is there a way in Glasgow Haskell to get a thread to wait on a child process
> in the same way as the Posix function wait(), and get the termination status
> of the child? If so, how?
This is what I use when I want to avoid that wait()ing for a
process in one thread blocks the whole Haskell runtime:
waitForExitCode pid = do
status <- do
status <- getProcessStatus False False pid
-- Note: With WNOHANG, waitpid() can have a return value of
-- 0 and still an `errno != 0'; the current
-- implementation of `getProcessStatus' doesn't handle
-- this case.
errno <- getErrorCode
if errno == noChildProcess
return $ Just (Exited ExitSuccess)
case status of
Nothing -> do
threadDelay 10000 -- wait 10ms
waitForExitCode pid vec
Just (Exited ec ) -> return ec
Just (Terminated sig) -> return $ ExitFailure (128 + sig)
Just _ -> -- can't happen, as second argument = `False'
error "Processes.proc: Stopped?"