[9fans] python read problem

[9fans] python read problem

[Michaelian Ennis]

I've noticed some behaviors I can't explain with python and plan9.  I
am using contrib/installed bichued/python.  Trying to read from a
serial port I would suspect I would have to use f.read() if I want to
be able to catch a specific string where there is no newline.

For instance:
When my firewall is finished booting it end with this output:

Type help or '?' for a list of available commands.
firewall>

"firewall>" being the command prompt.  I would expect to see the same from:

import sys
f = open("/dev/eia0","r")
while (True):
     sys.stdout.write(f.read(1))

Yet this only yields:
Type help or '?' for a list of available commands.

Which makes me think it is still looking for a newline.  Cons exhibits
the expected behavior with the same appliance. That is the prompt is
included.

ian

Re: [9fans] python read problem

[erik quanstrom]

> import sys
> f = open("/dev/eia0","r")
> while (True):
>      sys.stdout.write(f.read(1))
>
> Yet this only yields:
> Type help or '?' for a list of available commands.

have you tried redirecting the output of this to
a file, then using xd / wc to make sure that funny characters
aren't causing ... funny output?

- erik

Re: [9fans] python read problem

[Federico G. Benavento]

ok, con(1) does more than just dial, read and write,
it might also do rlogin...

does a C version of your script behave as expected?
what about dd -bs 1 -if  /dev/eai0 ?

as for new lines there's also a "rU" mode...

On Thu, Aug 26, 2010 at 9:18 PM, Michaelian Ennis <mennis@corvus.net> wrote:
> I've noticed some behaviors I can't explain with python and plan9.  I
> am using contrib/installed bichued/python.  Trying to read from a
> serial port I would suspect I would have to use f.read() if I want to
> be able to catch a specific string where there is no newline.
>
> For instance:
> When my firewall is finished booting it end with this output:
>
> Type help or '?' for a list of available commands.
> firewall>
>
> "firewall>" being the command prompt.  I would expect to see the same from:
>
> import sys
> f = open("/dev/eia0","r")
> while (True):
>     sys.stdout.write(f.read(1))
>
> Yet this only yields:
> Type help or '?' for a list of available commands.
>
> Which makes me think it is still looking for a newline.  Cons exhibits
> the expected behavior with the same appliance. That is the prompt is
> included.
>
> ian
>
>



-- 
Federico G. Benavento

Re: [9fans] python read problem

[Michaelian Ennis]

On Thu, Aug 26, 2010 at 10:04 PM, Federico G. Benavento
<benavento@gmail.com> wrote:

> what about dd -bs 1 -if  /dev/eai0 ?
This (while ridiculously slow) works correctly.

> as for new lines there's also a "rU" mode...

both
f = open("/dev/eia1","rU")
and
f = open("/dev/eia1","rU",0)

exhibit the same undesirable behavior.  As does when issuing f.flush()
before or after the f.read() in this loop.

ian

Re: [9fans] python read problem

[Fernan Bolando]

On Fri, Aug 27, 2010 at 8:18 AM, Michaelian Ennis <mennis@corvus.net> wrote:
> I've noticed some behaviors I can't explain with python and plan9.  I
> am using contrib/installed bichued/python.  Trying to read from a
> serial port I would suspect I would have to use f.read() if I want to
> be able to catch a specific string where there is no newline.
>
> For instance:
> When my firewall is finished booting it end with this output:
>
> Type help or '?' for a list of available commands.
> firewall>
>
> "firewall>" being the command prompt.  I would expect to see the same from:
>
> import sys
> f = open("/dev/eia0","r")
> while (True):
>     sys.stdout.write(f.read(1))
>
> Yet this only yields:
> Type help or '?' for a list of available commands.
>
> Which makes me think it is still looking for a newline.  Cons exhibits
> the expected behavior with the same appliance. That is the prompt is
> included.
>
> ian
>
>

Not sure but might be related.
in C you need do fflush because of the buffered io.