[Haskell-cafe] How to waitForProcess?

[Ivan Lazar Miljenovic]

On 5 September 2012 13:45, Magicloud Magiclouds
<magicloud.magiclouds at 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_
>
> --
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>
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>
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-- 
Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
http://IvanMiljenovic.wordpress.com