CODEWITHSUNDEEP
linuxshelltclkshexpect
user1121951
user1121951

Reputation:

expect + how to identify if expect break because time out?

The target of the following simple expect script is to get the hostname name on the remote machine

Sometimes expect script fail to perform ssh to $IP_ADDRESS ( because remote machine not active , etc )

so in this case the expect script will break after 10 second (timeout 10) , this is OK but......

There are two options

  1. Expect script perform ssh successfully , and performed the command hostname on the remote machine
  2. Expect script break because timeout was 10 seconds

On both cases expect will exit

but I don’t know if expect script perform ssh successfully or not?

is it possible to identify timeout process ? or to verify that expect ended because timeout?

Remark my Linux machine version - red-hat 5.1

Expect script

 [TestLinux]# get_host_name_on_remote_machine=`cat << EOF
  > set timeout 10
  > spawn  ssh   $IP_ADDRESS
  >            expect {
  >                      ")?"   { send "yes\r"  ; exp_continue  }
  > 
  >                      word:  {send $PASS\r}
  >                   }
  > expect >  {send "hostname\r"}
  > expect >    {send exit\r}
  > expect eof
  > EOF`

Example in case we not have connection to the remote host

 [TestLinux]# expect -c  "$get_host_name_on_remote_machine"
 spawn ssh 10.17.180.23
 [TestLinux]# echo $?
 0

Upvotes: 4

Views: 20102

Answers (2)

Donal Fellows
Donal Fellows

Reputation: 137567

To do sensible things on timeout, you need to tell expect what should happen:

set timeout 10
expect {
    ")?"     { send "yes\r"  ; exp_continue  }
    "word:"  { send "$PASS\r"                }
    timeout  { puts "timed out during login"; exit 1 }
}
set timeout -1   ; # Infinite...
expect ">"   { send "hostname\r"             }
expect ">"   { send "exit\r"                 }
expect eof
exit

Notice above how I use exit 1 when I hit an error. Your shell will be able to pick that up through $?, etc. (Without the 1 argument, the exit command will cause the script to terminate “successfully”; the same happens if you drop off the bottom of the script.)

Upvotes: 18

kostix
kostix

Reputation: 55443

Not really answering the original question, but why are you talking to SSH interactively when you just can pass it a script to execute? It's a shell after all.

I mean, just run:

ssh user@host '/usr/bin/hostname'

and ssh will spawn the hostname command remotely and connect its stdout to the stdout of the process which spawned ssh.

Back to the point—this looks like an example on how to bind an action to a timeout condition.

Upvotes: 4

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