Expect is not recognizing $expect_out(buffer) or $expect_out(0,string)

Question

I have Ubuntu 9.10 (and cannot change it in the near future due to testing) with expect5.45. Expect is working, but I have (at least) two issues. The first is that expect does not seem to be matching the string "password:". On my machine, the manual interaction appears as below:

root@Monkey2:~# rlogin $remoteAddress -l root
[email protected]'s password: 
Linux systest-desktop 2.6.31-22-generic #70-Ubuntu SMP Wed Dec 1 23:51:13 UTC 2010 i686

To access official Ubuntu documentation, please visit:
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Last login: Mon Jun 20 13:40:22 2011 from monkey2.local
root@systest-desktop:~# 

The contents of the script is as follows:

#!/usr/local/bin/expect -f

##  Connect to a neighboring linux box.
spawn ssh nn.nn.nnn.nnn -l root

expect "password:\n"

send "mypassword\n"

send "$expect_out(0,string)"

The script gets and displays the line requesting the password but times out. I've tried using "password:", "password: ", "password:\r" and password:*" but none seem to match.

---

The second issue is that the expect_out variable is not recognized and I get the following error when I run the script (whose name is 'this' and only has 11 lines!):

can't read "expect_out(0,string)": no such variable while executing "send "$expect_out(0,string)"" (file "this" line 18)

Answer 1

First thing to do when debugging expect programs is to add this line near the top:

exp_internal 1

That turns on (verbose) debugging output that shows what expect has seen from the spawned program, and how it matches your expect patterns.

Typically, one does something like this:

expect -re {password: $}
send -- "the_password\r"

You need to send a \r (a carriage return) instead of \n.