Line buffering pipes

Shaun Jackman sjackman at
Sat Oct 30 03:10:15 CEST 2004

I've found in help( 'open') that specifying 1 as the buffer size
indicates line buffering. I've tried this, but the same non-line
buffered behaviour persists. I've tried disabling buffering
altogether, specifying 0 as the buffer size, to no avail.

Python 2.3.4

Please cc me in your reply. Thanks,

On Fri, 29 Oct 2004 16:10:34 -0700, Shaun Jackman <sjackman at> wrote:
> I'm reading from a tcpdump pipe. I want to receive one line from the
> pipe as soon as its available from tcpdump. Something is buffering the
> pipe though, so I am receiving nothing, then multiple lines in a big
> batch. I thought this was the inherent buffering of next(), but it
> affects readline too.
> For example,
>     tcpdump = os.popen( 'sudo tcpdump', 'r')
> both
>     while True: print,
> and
>     while True: print tcpdump.readline(),
> buffer mutiple lines before printing.
> Please cc me in your reply. Thanks,
> Shaun

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