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expect(iing) via ssh to a down box

Posted by liderbug (liderbug), 19 July 2006
In an expect script ...
 send -- ssh $User@$Mach
 expect -exact word:

The problem is $Mach is down, the network is down, maint etc.  Ping works - ssh will just sit there.  I've got a semi dependable script.
set timeout 4
send -- ssh.....

   all piped to wc -c
motd will return right at 2000 char, failure about 400  followed by
if [ $n -gt 1000 ] exit 0 else exit 1

Any other ways to not get your computer hung?


Posted by admin (Graham Ellis), 19 July 2006
Yep, either put a timeout on it, or ping it first (but pinging it first may give you a false live if the remote machine is up but not running sshd for some reason).

If you have a lot of machines to try in parallel, ssh out to all of them and keep an id list so that all your timeouts are happening in parallel.\

Posted by liderbug (liderbug), 20 July 2006

I'm working on this:
typeset -i n
n=`${HOME}/bin/check_connect.exp $1 | wc -c`
if [ $n -gt 1000 ]
  echo "0"
  exit 0
  echo "1"
  exit 1
set Host   [lindex $argv 0]
set timeout 4
spawn $env(SHELL)
match_max 100000
send -- "ssh xxxxx@$Host\r"
expect -exact "word: "
send -- "*******\r"
expect -exact "> "
send -- "exit\r"
Then call the bash script and if return is 0 life is good, if it's "1" don't go there.    

Posted by admin (Graham Ellis), 20 July 2006
So .... rather than exactly expecting only "word" expect EITHER "word" or a timeout ... different actions on each.

See here for an example of the syntax.

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