runInteractiveProcess and buffering
lemming at henning-thielemann.de
Sat Oct 13 12:56:32 EDT 2007
On Fri, 12 Oct 2007, Adam Langley wrote:
> On 10/12/07, Henning Thielemann <lemming at henning-thielemann.de> wrote:
>> The data of 'out' seems to be buffered, because 'aseqdump' must produce
>> many lines until even the first one is returned by 'hGetLine' and printed
>> by 'putStrLn'. I tried to disable buffering for 'out' and indeed
>> 'NoBuffering' is printed to the terminal, but the output from 'aseqdump'
>> is still deferred.
> [I suspect this is a job for haskell-cafe@, anyway]
> Are you sure that you aseqdump isn't buffering itself?
I'm not sure, I only see that it works when started in a terminal. However
if I pipe it to 'less' then the output is deferred for a while. This seems
to indicate that the C program actually buffers itself. :-(
> The standard C libraries will buffer output at the line level at least,
> and are free to buffer much more than that if they think that the output
> is not to a terminal.
Is this decision done automatically by C's standard library or must the C
programmer do this manually? I couldn't find such a switch in the C
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