Proposal: overhaul System.Process

Simon Marlow marlowsd at
Tue May 27 04:22:20 EDT 2008

Duncan Coutts wrote:
> On Fri, 2008-05-16 at 15:44 +0100, Brian Brunswick wrote:
>> On Thu, May 15, 2008 at 10:45 AM, Simon Marlow <marlowsd at> wrote:
>>> The latest version of the Process overhaul is here:
>>>  - changes to readProcess, and added readProcessWithExitCode,
>>>    as discussed on the list.
>> I'd just like to argue briefly again against merging stdout and stderr.
> I think I agree. A more sensible default would be to discard stdout
> completely or to use the inherited stderr. Though exactly which depends
> on the context unfortunately.
> For Cabal we have a function like readProcess and it discards stderr.
> This seems to be the right thing for the various uses in Cabal (except
> stupid "python -V" which prints the version number to stderr).

Neil Mitchell and David Roundy argued against separating stdout and stderr 
for readProcessWithExitCode.  Myself I don't have a strong opinion - 
although I'm somewhat swayed by Brian's points.  It does seem slightly 
cleaner to separate the two in the default API.  Any more opinions?


More information about the Libraries mailing list