Can you tell me what is the problem here? Haskell app output is redirected to C++ input app (and vice-versa) using pipes. (used Erays shell script sugestion) When I try Hsk: 1. get, 2.send C++: 1. send, 2 get It works fine, but if I try it the other way around it locks. C++ app won't get any input. Seems to me like Hsk is not 'flushing' the output. If this is the case, I can't really explain why it happens... if the output was not redirected I am pretty sure that, before trying to get input the output would be flushed (imagine something like putStrLn "please type an int:") So what is the issue here? Here is the code, And once again, thanks in advance. J.A. ------------------------------- Haskell app: send -> get ------------------------------- main :: IO() main = do --send hsnum putStrLn "6" -- get cnum and save num <- readLn :: IO(Int) writeFile "./reshs.txt" (show num) ---------------------------- C++ app: get -> send ---------------------------- #include <cstdio> #include <iostream> #include <fstream> nt main(){ // *get* hsnum and save int num; ofstream out("rescc.txt"); cin >> num; out << num; // *send* cnum cout << 10 << '\n' << flush; //it works without the flush return 0; }