I probably should have also mentioned that the "fail" on windows is for me ssh-ed to that box remotely, where the sshd program is cygwin.

Thomas Hartman <thomas.hartman+external@db.com>
Sent by: haskell-cafe-bounces@haskell.org

08/28/2007 06:03 PM

To	haskell-cafe@haskell.org
cc
Subject	[Haskell-cafe] runInteractiveCommand behaves differently on linux and windows

Maybe this is by design, but I just thought I would point this behavior out and ask for comment.

test1 merely shows that runInteractiveCommand reacts differently to perl warnings than perl errors. Okay, maybe the inconsistency in that case is due to perl and not haskell.

test2 behaves the same on win and nix. This is "pipe like" in that the ouptut of a command (which could be the result of a shell call, but just as easily be the return of a haskell function) gets fed into a shell command. In this case, if the shell command is simply "tail" the behavior is consistent from win to nix.

test3 shows that the behavior stops being consistent if ssh enters the picture. (piping to tail via ssh). again, maybe this is due to ssh and not haskell.

however... note however that on windows

ghc -e 'mapM_ ( putStrLn . show ) [1..1000] ' | ssh `whoami`@localhost 'tail -n2'

works fine. so it's not *just* ssh, but ssh in conjuction with runInteractiveCommand which seems to cause problems

FWIW, using 10 lines instead of 1000 still hangs on windows.

Is there a way to code up shell pipelike behavior in a more portable way?

curious what the cafe thinks...

thomas.

import Test.HUnit
import Misc ( (>>=^) )
import System.Process
import System.IO
import System.Exit

-- works on linux, error on windows

test1 = do
res1 <- test_shellrunStderrOk
runTestTT $ TestCase ( assertEqual "test1" "made it" res1 )
where test_shellrunStderrOk = do
runprocessStdErrAllowed' "" cmdPerlwarn
return "made it"
cmdPerldie = " perl -e 'die \"error\"' "
cmdPerlwarn = " perl -e 'warn \"blee\"' "

-- works on linux, windows
test2 = pipeTo "tail -n2"

-- works on linux, hangs on windows
test3 = pipeTo "ssh `whoami`@localhost 'tail -n2'"

pipeTo cmd = do
res2 <- test_shellrunPipeinLike
runTestTT $ TestCase ( assertEqual ( "pipe to, cmd: " ++ cmd) (show l) res2 )
where test_shellrunPipeinLike = do
runprocessStdErrAllowed' (unlines $ map show [1..l]) ( cmd )
>>=^ filter (not . ( == '\n') )
l = 1000

runprocessStdErrAllowed' inp s = do
(ih,oh,eh,pid) <- runInteractiveCommand s
so <- hGetContents oh
se <- hGetContents eh
hPutStrLn ih inp
hClose ih
ex <- waitForProcess pid
case ex of
ExitFailure e -> fail $ "shell command " ++ s ++ "\nFailed with status: " ++ show e
_ | otherwise -> return so

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