[Haskell-cafe] using an external application
spy.hunter at email.cz
Fri Nov 2 04:17:23 EDT 2007
I'm solving the following problem - I need to use an external
application - give it the input data and receive its output.
However, when multiple calls are made, the results are not
as expected. The simplified version of the problem is given
main = do
System.Cmd.system "echo hello >output.txt" -- use the external
application to create an output file
o1 <- readFile "output.txt"
System.Cmd.system "echo bye >output.txt" -- the second call to
the external application
o2 <- readFile "output.txt"
putStr o1 -- "hello" expected, but "bye" printed
Can you please give me some hint to solve this problem?
I'm a beginning haskell developer and I'm still a bit confused
by the IO monad.
Thank you in advance.
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