On 19 April 2005 06:30, Johannes Waldmann wrote:
> Thanks for the comments. Indeed I knew the solution -
> once I isolated the problem.
>
> Note that ghc(i) behaves differently when running main2 below
> (it says "file is locked"). (hugs does not complain.)
>
> import System
>
> main1 = do
> system "echo A > foo"
> a <- readFile "foo"
> system "echo B > foo"
> b <- readFile "foo"
> print (a == b)
>
> main2 = do
> writeFile "foo" "A"
> a <- readFile "foo"
> writeFile "foo" "B"
> b <- readFile "foo"
> print (a == b)
GHC is correct to complain about main2, FWIW. The Haskell report
specifies single-writer/multiple-reader locking on files.
Cheers,
Simon
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