[Haskell-cafe] struggling with blocking shell cmd when using System.Process

Brandon Allbery allbery.b at gmail.com
Tue Mar 20 23:15:20 CET 2012

On Tue, Mar 20, 2012 at 17:51, Rouan van Dalen <rvdalen at yahoo.co.uk> wrote:

> If I try to su the runShell function with the following command, it simply
> blocks forever:
>     git --no-pager blame <your git file here>
> but if I do:
>     git status
> The runShell function works as expected.  Can someone shed some light on
> why the 'git blame' command blocks?  Interrestingly enough, if I

You're trying to run the command and then collect all the output afterward;
this requires the OS to buffer potentially very large amounts of data,
whereas most OSes cache only a very small amount over a pipe.  You will
need to read the data as the command runs to avoid blocking, then close the
process once you have read EOF.

brandon s allbery                                      allbery.b at gmail.com
wandering unix systems administrator (available)     (412) 475-9364 vm/sms
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