Petr Hoffmann writes:
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 below:
System.Cmd.system "echo hello >output.txt" -- use the external
...
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.
I have the impression that your problem has nothing to do do with Haskell, you just rewrite your file, instead of appending to it. But perhaps I didn't look correctly... Jerzy Karczmarczuk