Update examples

testsuite/dynload/io/TestIO.hs

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+{-# OPTIONS -fglasgow-exts -cpp #-}
+--
+-- Copyright (c) 2004 Don Stewart - http://www.cse.unsw.edu.au/~dons
+-- LGPL version 2.1 or later (see http://www.gnu.org/copyleft/lesser.html)
+--
+
+module TestIO ( resource_dyn )  where
+
+import API
+import AltData.Dynamic
+
+import System.IO
+import System.Posix.Types   ( ProcessID, Fd )
+import System.Posix.Process ( forkProcess, executeFile, getProcessID )
+import System.Posix.IO      ( createPipe, stdInput, 
+                              stdOutput, fdToHandle, closeFd, dupTo )
+
+resource_dyn :: Dynamic
+resource_dyn = toDyn resource
+
+resource :: TestIO
+resource = testio { field = date }
+
+
+--
+-- call a shell command , returning it's output
+--
+date :: IO String
+date = do (hdl,_,_) <- catch (popen "/bin/date") (\_->error "popen failed")
+          hGetLine hdl 
+
+------------------------------------------------------------------------
+--
+-- my implementation of $val = `cmd`; (if this was perl)
+--
+-- provide similar functionality to popen(3), 
+-- along with bidirectional ipc via pipes
+-- return's the pid of the child process
+--
+-- there are two different forkProcess functions. the pre-620 was a
+-- unix-fork style function, and the modern function has semantics more
+-- like the Awkward-Squad paper. We provide implementations of popen
+-- using both versions, depending on which GHC the user wants to try.
+-- 
+
+popen :: FilePath -> IO (Handle, Handle, ProcessID)
+popen cmd = do
+        (pr, pw) <- createPipe
+        (cr, cw) <- createPipe    
+
+        -- parent --
+        let parent = do closeFd cw
+                        closeFd pr
+        -- child --
+        let child  = do closeFd pw
+                        closeFd cr 
+                        exec cmd (pr,cw)
+                        error "exec cmd failed!" -- typing only
+
+-- if the parser front end understood cpp, this would work
+-- #if __GLASGOW_HASKELL__ >= 601
+        pid <- forkProcess child -- fork child
+        parent                   -- and run parent code
+-- #else
+--          p   <- forkProcess
+--          pid <- case p of
+--                  Just pid -> parent >> return pid
+--                  Nothing  -> child
+-- #endif
+
+        hcr <- fdToHandle cr
+        hpw <- fdToHandle pw
+
+        return (hcr,hpw,pid)
+
+--
+-- execve cmd in the child process, dup'ing the file descriptors passed
+-- as arguments to become the child's stdin and stdout.
+--
+exec :: FilePath -> (Fd,Fd) -> IO ()
+exec cmd (pr,cw) = do
+        dupTo pr stdInput
+        dupTo cw stdOutput
+        executeFile cmd False [] Nothing
+
+------------------------------------------------------------------------