Yes, the automatic closing of handles has confused me as well when I wrote Proctest:
http://hackage.haskell.org/packages/archive/proctest/latest/doc/html/Test-Proctest.html It might contain useful examples on how to deal with processes. Niklas On 15/11/12 14:42, Herbert Valerio Riedel wrote: > rnons <remotenonse...@gmail.com> writes: > > [...] > >> mpgLoop = do >> let sh = "mpg123 -R" >> (Just hin, Just hout, _, hdl) <- createProcess (shell sh){ std_in = >> CreatePipe, std_out=CreatePipe } >> --hPutStrLn hin "SILENCE" >> hPutStrLn hin "LOAD /home/rnons/Music/test.mp3" >> hFlush hin >> waitForProcess hdl >> return () > > [...] > >> I expected with "waitForProcess", this program will be able to run >> till the song ends. However, mpg123 plays for only 6 seconds. >> >> Maybe I missed something? > > Just a guess: the problem may be that "a Handle will be automatically > closed when the garbage collector detects that it has become > unreferenced by the program"[1], and in the program above, the liveness > of the hin/hout references ends before mpg123 is finished playing. And > 'mpg123 -R' shuts down as soon as it detects its stdin (or stdout) > getting EOF... so that's what you're experiencing most likely here. > > Try to keep hin/hout "alive" a bit longer, and mpg123 should survive > longer. Also you should most probably consume the output comming from > 'mpg123 -R' via 'hout', as otherwise it the buffer might build up and > mpg123 might block. > > hth, > hvr > > [1]: > http://hackage.haskell.org/packages/archive/base/4.6.0.0/doc/html/System-IO.html#t:Handle > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
