oxware:

I use "system" in System.Cmd to execute a shell cmd, then how can I catch its stdout?

Use System.Process, http://haskell.org/ghc/docs/latest/html/libraries/base/System-Process.html And example, call the 'date' program:

(inh,outh,errh,pid) <- runInteractiveProcess "date" ["+%d:%m:%y"] Nothing Nothing hClose inh hGetContents outh "24:01:07\n"

Regards, Don There's some wrappers to this floating around too, which should get into base soon enough.. E.g. http://www.cse.unsw.edu.au/~dons/code/newpopen/