[darcs-devel] darcs patch: Fix Windows stderr non-redirection. (and 1 more)

[Jason Dagit]

On 9/9/06, Eric Y. Kow <eric.kow at gmail.com> wrote:
> On Sat, Sep 09, 2006 at 22:10:14 +0200, Tommy Pettersson wrote:
> > Anyway, I had some difficulty reading the code (most of the code
> > in Exec.lhs), so I tried to make it more readable, which (for me
> > at least) means more simple.  So I only kept one version of exec (the
> > fancy one, but with the name exec), and used the redirection data type
> > all the way. This is merely a suggestion, for now -- "easy to read" is
> > very subjective.
>
> I think this is an improvement.  Thanks!
>
> > I have changed the
> > Windows code too, but have not tried to compile it since I don't
> > have Windows.
>
> I have a trick for that.  I just set #define WIN32 (after recording
> the patch so I can easily revert it)
>
> Alright, so this patch is waiting for two things
>
> 1) Eric - find Juliusz's message re: stderr redirection
>    (I assume it's not the message where he accepted my patch)
>    I would be happy for stderr to NOT be redirected by
>    default, but just want to double-check the arguments,
>    just to be conservative and avoid changing behaviour
>    unless necessary.
>
> 2) A windows user - confirmation or denial
>    Windows automatically redirects stderr when stdout is redirected,
>    unless stderr is explicitly redirected somewhere.
>    (That sounds like a silly behaviour!)

I just used a program:

-----------------
import System.IO

main :: IO ()
main = do hPutStrLn stdout "writing to stdout..."
          hFlush stdout
          hPutStrLn stderr "writing to stderr..."
          hFlush stderr
------------------

And generated the following:
H:\>main.exe
writing to stdout...
writing to stderr...

H:\>main.exe > out.txt
writing to stderr...

H:\>type out.txt
writing to stdout...

H:\>main.exe 2> out2.txt
writing to stdout...

H:\>type out2.txt
writing to stderr...

H:\>main.exe 2>>&1 > out3.txt
writing to stderr...

So from my 2 minute expirement I see it's possible to redirect them
separately but I don't understand how to redirect them at the same
time.

HTH,
Jason