Reading input from a system command in Haskell

hi I need to read the command line standard out after executing a haskell command, i know there are two modules to execute system commands: System.Cmd and System.Process

can anybody show me a simple example how to run the System.Process functions?

here is a example what i need to do (i know there is System.Directory to do that but i thought this is a good example):

1. execute a system co开发者_如何学Pythonmmand like ls -a
2. now i dont want the user to see the output
3. the output should only be accessable in my program to validate it

how can i do that?

import System.Process
test = readProcess "ls" ["-a"] ""

Do refer to the documentation for usage details.