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