Help with regex on telnet output

[Eddie Corns]

Adam Flott <adam at npjh.com> writes:

>I'm having some difficulty getting the expect function of telnetlib to
>capture some data that gets returned from a telnet connection.

>Python's telnet debug reports this:

>recv 'whoami\n\r\xff\xfc\x01\r\nHi, my name is :     Home\r\nHere'
>IAC WONT 1
>recv ' is what I know about myself:\r\nModel:             '
>recv '  VSX 7000\r\nSerial Number:       822232085C63K\r\nS'
>recv 'oftware Version:    Release 1.0 - August 2001\r'
>recv '\nBuild Information:   build at www.'
>recv 'a.com\r\nFPGA Revision:       4.3.0\r\nMain Proc'
>recv 'essor:      BSP15   v0.0 ~ Core/Mem Clks 415/111  '
>recv '[3:4 0:3]\r\nTime In Last Call:   0:00:00\r\nTotal Tim'
>recv 'e In Calls: 0:22:17\r\nTotal Calls:         18\r\nSNTP'
>recv ' Time Service:   auto insync 21.1.1.1\r\nLocal Tim'
>recv 'e is:        Mon,  5 Jul 2004 20:59:35 -0500\r\nNetw'
>recv 'ork Interface:   ISDN_QUAD_BRI\r\nIP Video Number:  '
>recv '   192.168.0.99\r\nISDN Video Number:   1.555.115047'
>recv '4\r\nH323 Enabled:        True\r\nFTP Enabled:        '
>recv ' True\r\nHTTP Enabled:        True\r\nSNMP Enabled:   '
>recv '     True\r\nNIC Slot 1 SW Ver:   6.03\r\nNIC Slot 1 B'
>recv 'oot Ver:   0.02\r\n\xff\xfb\x03'
>IAC WILL 3
>recv '\xff\xfc\x01'
>IAC WONT 1
>recv '\xff\xfb\x03'
>IAC WILL 3

>The call I made to expect including a timeout of 1 seconds, which is
>plenty of time to wait for a response, but keeps repeating WILL 3/WONT 1
>indefinitely. 

>I only want to match from the begginning (\r\nHi. to the end 0.02\r\n).
>This data is not specific and I just want data that looks like this
>format to be returned from the call to expect. The only thing I've found
>that is constant is a colon separates one side to the other.

>Here is the start to the regular expression I've been trying to get to
>work:

>"^([\w\s]+?)(:)\s{1,}(.*):?\r\n$"

The first thing to note is that expect does not MATCH in quite the same sense
as when matching a string.  What it does is match all the input from where it
last left off until the point in the stream when the regex matches. eg:

if the stream looks like:

  "$ whereami\nYou are here.\n$ "

and you match on "a.e", it will return "$ whereami\nYou are".  The next read()
or expect() call will start from "here.\n$ "

You would need to either pull out the portion you want from within that or
more usually make sure you've matched up to the start.  Secondly the ^ and $
don't really make sense on a stream ($ will certainly cause it to hang; not
sure why timeout doesn't fix that).

I generally try to use read_until() instead of expect(), this only works if
you have well defined strings you can match on eg. "Hi, my name is" to get the
start or better still match on the echo of the command you sent, and the user
level prompt to finish (there doesn't seem to be a prompt in your trace
though).  At worst you can use timeouts to know when it's done.

Fixed strings leads to more robust applications and easier to read code IMHO.

Eddie