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System.IO.openFile seems to have inconsistent behaviour across platforms regarding file sharing permissions.

Given this program:

{-# LANGUAGE CPP #-}

import System.IO
import System.Process

main = do
    h <- openFile "file.txt" WriteMode
    hPutStrLn h "Success! I can see the file's contents."
    hFlush h
#ifdef mingw32_HOST_OS
    system "type file.txt"
#else
    system "cat file.txt"
#endif
    hClose h

Running under Ubuntu 10.04 / GHC 6.12.1, I get:

$ runghc openFile.hs
Success! I can see the file's contents.

Running under Windows 7 / GHC 6.12.3, I get:

> runghc openFile.hs
The process cannot access the file because it is being used by another process.

In my opinion the behaviour exhibited by Linux is preferable because it allows for log files to be written by long running processes. These log files can then be inspected externally while the Haskell process is still running.

The Snap Framework (snapframework.com) does this and it works great on Linux / Mac OS, but on Windows the log files cannot be viewed until after the server is shut down.

Trac metadata

Trac field	Value
Version	6.12.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/base
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