[Haskell-cafe] How to waitForProcess?
Hi, I have code like this and it leaves lots of zombies of flow-export. Then I add waitForProcess Well I do not know where to put it. Before or after 'hGetContents' both make the program hung. exportCSV :: FilePath - IO [String] exportCSV file = do csv_ - withBinaryFile file ReadMode $ \i - do (_, Just o, _, h) - createProcess $ CreateProcess (RawCommand /usr/bin/flow-export [-f2]) Nothing Nothing (UseHandle i) CreatePipe Inherit True False hGetContents o return $ tail $ lines csv_ -- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to waitForProcess?
On 5 September 2012 13:45, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, I have code like this and it leaves lots of zombies of flow-export. Then I add waitForProcess Well I do not know where to put it. Before or after 'hGetContents' both make the program hung. You're probably being bitten by hGetContents being lazy. Force the result of hGetContents (e.g. `evaluate . length = hGetContents o ') and then use waitForProcess. exportCSV :: FilePath - IO [String] exportCSV file = do csv_ - withBinaryFile file ReadMode $ \i - do (_, Just o, _, h) - createProcess $ CreateProcess (RawCommand /usr/bin/flow-export [-f2]) Nothing Nothing (UseHandle i) CreatePipe Inherit True False hGetContents o return $ tail $ lines csv_ -- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to waitForProcess?
You might have to use hGetContents, then waitForProcess, and then terminateProcess -- you can then check if the process is indeed terminated using getProcessExitCode. On Wed, Sep 5, 2012 at 1:45 PM, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, I have code like this and it leaves lots of zombies of flow-export. Then I add waitForProcess Well I do not know where to put it. Before or after 'hGetContents' both make the program hung. exportCSV :: FilePath - IO [String] exportCSV file = do csv_ - withBinaryFile file ReadMode $ \i - do (_, Just o, _, h) - createProcess $ CreateProcess (RawCommand /usr/bin/flow-export [-f2]) Nothing Nothing (UseHandle i) CreatePipe Inherit True False hGetContents o return $ tail $ lines csv_ -- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com. ___ 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
Re: [Haskell-cafe] How to waitForProcess?
Forgot about that, just read 'readProcess' code to figure out. Thanks. On Wed, Sep 5, 2012 at 12:37 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com wrote: On 5 September 2012 13:45, Magicloud Magiclouds magicloud.magiclo...@gmail.com wrote: Hi, I have code like this and it leaves lots of zombies of flow-export. Then I add waitForProcess Well I do not know where to put it. Before or after 'hGetContents' both make the program hung. You're probably being bitten by hGetContents being lazy. Force the result of hGetContents (e.g. `evaluate . length = hGetContents o ') and then use waitForProcess. exportCSV :: FilePath - IO [String] exportCSV file = do csv_ - withBinaryFile file ReadMode $ \i - do (_, Just o, _, h) - createProcess $ CreateProcess (RawCommand /usr/bin/flow-export [-f2]) Nothing Nothing (UseHandle i) CreatePipe Inherit True False hGetContents o return $ tail $ lines csv_ -- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com -- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to waitForProcess?
On Tue, Sep 4, 2012 at 9:39 PM, Mike Ledger eleventyn...@gmail.com wrote: You might have to use hGetContents, then waitForProcess, and then terminateProcess -- you can then check if the process is indeed terminated using getProcessExitCode. Er? When waitForProcess returns the process is dead; there's nothing to terminateProcess. If you do it the other way around then you may not get full output. For starters, I would not build up the CreateProcess record directly but use the proc record and override it with your I/O definitions. I've been bit by this before (I think some older version of System.Process lacked useful predefined records?). There is a severe gotcha here if you do things naively (like your example code does). If there is more output than will fit in a pipe, *no* ordering of read / wait in a single thread will work without deadlocking; you have no choice but to do the read in a separate thread. This is not a Haskell issue, it is how pipes work on POSIX systems. (I don't know if Windows has the same problem.) -- brandon s allbery allber...@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
