On 16/11/2010 06:52, Ton wrote:
On Nov 16, 1:47 am, MRAB<pyt...@mrabarnett.plus.com> wrote:
On 15/11/2010 11:03, Ton wrote:
On Nov 14, 11:55 pm, MRAB<pyt...@mrabarnett.plus.com> wrote:
On 14/11/2010 14:48, ton ph wrote:> Hi python geeks,
I have problem which i have been trying to find out for the past
some days, i have a device which feeds info to my fifo continuosly, and
a thread of mine reads the
fifo continuosly. Now when i change a parameter in the device, it sends
me different values. Now my problem is that , i want to get rid of the
contents of my previous info which
is present in my buffer of the fifo.So i want to flush the fifo content
when my device starts sending different info .... i am implementing
writing and reading the fifo using two different threads.
Please someone guide me solving my problem.
I highly apologise everyone in case my post is not so clear...
Thanks everyone in advance.
When the info changes, the thread which is putting items into the fifo
could flush it just by getting items from it (using a non-blocking get)
until it's empty.
Hi Mrab,
Thanks for your immediate reply , can you please guide me with any
tool or library function which i can flush my fifo content .. i use
os.mkfifo() to make the fifo. Or is there any other way i could do
this ...
Thanks
Ah, you're using pipes; I thought you might've been using a queue. I
don't know of a way of flushing a pipe.
I wonder whether it's a good idea for the producer to keep filling the
fifo, because the consumer know how 'old' the info is when it arrives,
and there's your problem of discarding stale info. Perhaps the producer
should wait until the consumer has sent an acknowledgement before
sending more info.
Thanks Mrab,
the problem now is that the producer continously dumps the
information and since i am implementing the producer using the
subprocess as like this
cmd = ['my files']
proc = subprocess.Popen(cmd, shell=True, bufsize=0,
stdout=subprocess.PIPE, stderr=subprocess.STDOUT )
while flag == True:
line = proc.stdout.read()
Now what i want is to synchronise the problem of actual info the
device is sending and the proper reading as the device is sending and
not about reading the previous old info in the fifo... hope i have
made clearer my prob. even i have tried proc.stdout.flush(), to flush
the previous old info in the fifo. Thnks
Use two pipes, one each way. The consumer could use send a message to
the producer requesting an update, which the producer could send back
via the other pipe.
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