Forgot about that, just read 'readProcess' code to figure out. Thanks. On Wed, Sep 5, 2012 at 12:37 PM, Ivan Lazar Miljenovic wrote:

On 5 September 2012 13:45, Magicloud Magiclouds 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_

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-- 竹密岂妨流水过 山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

On Tue, Sep 4, 2012 at 9:39 PM, Mike Ledger 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 allbery.b@gmail.com wandering unix systems administrator (available) (412) 475-9364 vm/sms