Here’s some simple code I put together. I’m mostly posting it so I won’t have any problems finding it in the future.
module Main where import Control.Monad import System.Exit import System.Posix.IO import System.Posix.Process executeChild = do mapM_ closeFd [stdInput, stdOutput, stdError] devnull <- openFd "/dev/null" ReadWrite Nothing defaultFileFlags dup devnull; dup devnull executeFile "./Child" False  Nothing main = do child <- forkProcess executeChild putStrLn "ForkExec: main - forked, going to wait" s <- getProcessStatus True True child case s of Nothing -> -- this shouldn't happen, ever print s >> exitFailure Just s -> do print s case s of Exited _ -> putStrLn "Child exited properly, though possibly unsuccessfully" Terminated _ -> putStrLn "Terminated!" Stopped _ -> putStrLn "Stopped (only SIGSTOP?)" exitSuccess exitFailure
It’d be really nice to be able to, after the fork, close all open file descriptors in the child. But how can I find all the open file descriptors in a process? Ideally it should be fairly portable, though portability to major Unix/Linux systems is enough for me.