[Tutor] Pexpect maxread & searchwindowsize, timeout

[Nathan Farrar]

Thanks!  That solves my question about configuring the timeout value.
However - I still have the problem (I believe) that by default, I can
handle all the output.  When I issue the "show version" it fails, but
if I issue a command with less data returned it succeeds.

In the documentation I can see that pexpect uses a maxread and a
searchwindowsize value, but I'm not sure how to use them.

Any tips?  Thanks again.

On Tue, Oct 20, 2009 at 11:26 AM, vince spicer <vinces1979 at gmail.com> wrote:
>
>
> On Tue, Oct 20, 2009 at 11:11 AM, Nathan Farrar <nathan.farrar at gmail.com>
> wrote:
>>
>> I haven't been able to find any real examples of pexpect usage, nor
>> documentation.  Just little bits here and there, so I'm kind of
>> struggling through.
>>
>> I've got the follow bit of code I'm working with:
>>
>> def main():
>>    try:
>>        print 'attempting to spawn connection ... '
>>        session = pexpect.spawn('ssh username at x.x.x.x')
>>    except:
>>        print 'couldn\'t spawn connection ... '
>>
>>    print 'waiting for password prompt ... '
>>    session.expect('password:')
>>    print 'received password prompt ... '
>>
>>    try:
>>        print 'attempting to send password ... '
>>        session.sendline(password)
>>    except:
>>        print 'error sending password ... '
>>
>>    print 'waiting for command prompt ... '
>>    session.expect(command_prompt)
>>    print 'received command prompt ... '
>>
>>    try:
>>        print 'attempting to issue \'show version\' command ... '
>>        session.sendline([expect.TIMEOUT=1, 'show version'])
>>    except:
>>        print 'error issuing \'show version\' command ... '
>>
>>    print 'waiting for command prompt ... '
>>    session.expect(command_prompt)
>>    print 'received command prompt ... '
>>
>>    print 'attempting to print command results ... '
>>    print session.before
>>
>>    print 'closing session ... '
>>    session.close()
>>
>> if __name__=='__main__':
>>    main()
>>
>> When I run this against a cisco device, it times out waiting for the
>> command prompt after issuing the show version command.  However, if I
>> change 'show version' to something like 'blah blah' it doesn't time
>> out, and I get the results of the command (an error message that is
>> much shorter in length).
>>
>> I believe that the results of the show version command are simply too
>> large.  I think I may need to increase the size of maxread &
>> searchwindowsize & set the timeout to something lower than the
>> default, but I haven't been able to figure out how to do this
>> correctly yet.
>>
>> Any help would be greatly appreciated.  I'm pulling my hair out.  Thank
>> you.
>>
>> --
>> "The presence of those seeking the truth is infinitely to be preferred
>> to the presence of those who think they've found it."
>>
>> –Terry Pratchett
>> _______________________________________________
>> Tutor maillist  -  Tutor at python.org
>> To unsubscribe or change subscription options:
>> http://mail.python.org/mailman/listinfo/tutor
>
> Looks like you are trying to end multiple commands to the sendline and not
> expect
> you can specify the timeout on the expect line
>
> try this code:
>
> #================================================
>
> def main():
>    try:
>        print 'attempting to spawn connection ... '
>        session = pexpect.spawn('ssh username at x.x.x.x')
>    except:
>        print 'couldn\'t spawn connection ... '
>
>    print 'waiting for password prompt ... '
>    session.expect('password:')
>    print 'received password prompt ... '
>
>    try:
>        print 'attempting to send password ... '
>        session.sendline(password)
>    except:
>        print 'error sending password ... '
>
>    print 'waiting for command prompt ... '
>    session.expect(command_prompt)
>    print 'received command prompt ... '
>
>    try:
>        print 'attempting to issue \'show version\' command ... '
>        session.sendline('show version') #: send only command
>    except:
>        print 'error issuing \'show version\' command ... '
>
>    print 'waiting for command prompt ... '
>    session.expect(command_prompt, timeout=1) #: set the timeout here
>    print 'received command prompt ... '
>
>    print 'attempting to print command results ... '
>    print session.before
>
>    print 'closing session ... '
>    session.close()
>
> if __name__=='__main__':
>    main()
> #==============================
>
> Vince
>
>
>



-- 
"The presence of those seeking the truth is infinitely to be preferred
to the presence of those who think they've found it."

–Terry Pratchett