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