bug in System.system on ghc-6.2.1

[Simon Marlow]

On 20 July 2004 13:39, Malcolm Wallace wrote:

> Using the glibc-2.2 (RedHat 7) Linux binary package of ghc-6.2.1,
> the following program:
> 
>     import System.Cmd
>     main = do v <- system("ghc --version 2>&1")
>               print v
> 
> incorrectly gives
> 
>     ExitFailure 127

Are you sure your shell understands the '>&' syntax?  Not all do.

> whereas with the glibc-2.3 Linux binary package of ghc-6.2.1, the
> same program correctly gives
> 
>     The Glorious Glasgow Haskell Compilation System, version 6.2.1
>     ExitSuccess

Assuming you're using the same shell in both cases, this could indicate
a problem somewhere.  Could you try strace on the binary?

> If we change the use of "system" to "rawSystem", both versions work
> fine. 
> 
>     import System.Cmd
>     main = do v <- rawSystem "ghc" ["--version","2>&1"]
>               print v
> 
> However, rawSystem is not portable across compiler implementations,
> whereas System.system is supposed to be.

The '2>&1' will be passed as a raw argument to GHC in this case.
Fortunately GHC is ignoring it.

Cheers,
	Simon