Crash using 'default' shell prompt setting

2012-05-04T04:37:22Z

On Ubuntu 12.04:

apt-cache policy expect-lite
expect-lite:
Installed: 4.2.0-0ubuntu1
Candidate: 4.2.0-0ubuntu1

I use expect-lite scripts from cron tasks to query the line quality of ADSL modems using telnet sessions. I've had a script running successfully for external Speedtouch 610 for a long time without problems.

Recently I deployed a server with an internal PCI-ADSL2+ modem based on the Infineon Danube - this is a MIPS SoC that presents to the host PC as a standard Ethernet interface and runs embedded Linux 2.4.31 with telnetd and BusyBox.

I created an expect-lite script for it but see a crash caused by expect-lite incorrectly trying to set a shell prompt:

---- danube-pci-adsl.elt -----
#!/usr/bin/expect-lite -f
# connect to Danube PCI ADSL Modem and get connection quality
@30
*EOLS LF
*INTERACT
---- EOF -----

The result is:

$ EL_CONNECT_METHOD=telnet EL_CONNECT_USER=root EL_CONNECT_PASS=12345678 EL_REMOTE_HOST=modem ./danube-pci-adsl.elt
spawn /usr/bin/telnet modem
Trying 10.254.249.1...
Connected to modem.
Escape character is '^]'.
Danube login: root
Password:

Setting Expect Timeout to: 30

expect-lite directive: *EOLS LF

expect-lite directive: *INTERACT

Press '+++' to end interact session & return to script

export PS1='$ '
set prompt = "$ "

BusyBox v1.00 (2008.08.04-09:35+0000) Built-in shell (msh)
Enter 'help' for a list of built-in commands.

#
# export PS1='$ '
$ set prompt = "$ "
getcell(0)
Connection closed by foreign host.
CONNECT ERROR: Unable to connect to remote_host: modem
send: spawn id exp6 not open

The problem is that sending

set prompt = "$ "

isn't safe for the msh shell implemented by BusyBox. A workaround is to force setting of an alternate shell prompt even though it won't be understood by msh.

expect-lite should not try to set a prompt for a shell it doesn't recognise.

dynamic variables only support "$ " prompt

2007-11-27T16:50:41Z

Hi,

A "% " prompt will not match dynamic variables. I think only "$ " will work. ("$" - with no space - will not find the prompt at all.

A workaround - put at the top of elt file:

>PS1="$ ";echo;
<\$

Details:

cat test.elt
; ==== Ping localhost and report result ====

@5
>echo a b c
##<a b c
+$packet_rx=a b (c)
>
>echo "Packets received are:$packet_rx"

This works:

PS1="$ "
$
$
$ expect-lite r=none c=test.elt
Warning: Remote Host=none, using Localhost
spawn bash

$
$
$ bash
$
$

==== Ping localhost and report result ====

Setting Expect Timeout to: 5

$
$ echo a b c
a b c
$
Assigned Var:packet_rx=c

$
$ echo "Packets received are:c"
Packets received are:c
$

##Overall Result: PASS

Not work:

$ PS1="$"
$expect-lite r=none c=test.elt
Warning: Remote Host=none, using Localhost
spawn bash

$
$

ERROR: Unable to detect prompt, connection appears to be dead.
$
$
$PS1="$ "
$ expect-lite r=none c=test.elt
Warning: Remote Host=none, using Localhost
spawn bash

$
$
$ bash
$
$
$
$
==== Ping localhost and report result ====

Setting Expect Timeout to: 5

echo a b c
a b c
$
Assigned Var:packet_rx=c

$
$

##Overall Result: PASS

Not work:

$ PS1="% "
% expect-lite r=none c=test.elt
Warning: Remote Host=none, using Localhost
spawn bash

%
%
% bash
%

==== Ping localhost and report result ====

Setting Expect Timeout to: 5

%
%
% echo a b c
a b c
% Warning: Expect-lite: Var Capture Timed Out! Recommend lengthening timeout, current timeout is: 5 secs

% echo "Packets received are:__NO_STRING_CAPTURED__"
Packets received are:__NO_STRING_CAPTURED__
%

##Overall Result: PASS

Thanks,

-Herb

herbert_marti@yahoo.com

PS: I think this expect-lite has a lot of potential for bash scripting. Thanks!

Recent changes to bugs

Crash using 'default' shell prompt setting

dynamic variables only support "$ " prompt