not so talkative expect

I'm not sure how I could miss it, but just recently I learned how to set expect not to send everything to the standard output. In the expect file you have to set log_user 0. you can change it but by log_user 1.

This is very helpful to write bash scripts i.e. using my remote_command.expect script - awking output is much easier.

Expect, telnet and Dell switch

Recently I've tried to find a way to obtain MAC addresses of computers attached to a Dell Switch. I've found that i.e. show bridge address-table ethernet 1/g3 returns  MAC addresses behind the port 3. I found small problem - it's not so easy to query all ports (or a chosen set of ports). Therefore, I decided to use expect. You can find the script below.
It connects to a switch run the command and finally print a mac address in the format with ':' between number doublets.
However, there are two issues. I don't know how to avoid sending everything to the standard output. Moreover, if there are more than one MAC address connected to the port (i.e. virtual machines), only first address will be print on the bottom of the output. To be precise the address  appears in the line 6 of output (see line started with set temp_mac).

#!/usr/bin/expect -f

set timeout -1

set machine [lindex $argv 0]
set port [lindex $argv 1]
set command "show bridge address-table ethernet 1/g$port\n"

#Connect to the server
spawn telnet $machine 

expect "User:"
exp_send "admin\r"
expect "Password:"
exp_send "myXEN\r"
expect "?*>"
exp_send "enable\r"
expect "?*#"
exp_send $command
expect "?*#"
set temp_mac [ lindex [ lindex [ split $expect_out(0,string) "\n"] 6] 1]
exp_send "exit\r"
exp_send "quit\r"

puts "\n"

# Creating mac address in DHCP format (with ':')
set mac [ string range $temp_mac 0 1 ]
append mac "."
append mac [ string range $temp_mac 2 6 ]
append mac "."
append mac [ string range $temp_mac 7 11 ]
append mac "."
append mac [ string range $temp_mac 12 13 ]

puts  "$machine/$port:  [ string map  {. :} $mac]"

exit

Oh one more thing. To make a list of all following it's good to run the script in loop and the following one should be good base to start with.

for ((i=1;i<48;i++)) do mac-dell.expect esw44-1 $i| grep "esw44-1/$i"; done

Expect, ssh and two passwords

Let say that you need to run a command on many remote machine and you cannot use any of specialist tools (I mean i.e. func). In such situation expect might be helpful and I even has written about it already. Recently I had to modified my script, cause not all remote systems have the same root password.

#!/usr/bin/expect -f

set timeout -1

set machine [lindex $argv 0]
set command [lindex $argv 1]

set pass "xen4ulez\r" 
puts $machine

spawn ssh -o "NumberOfPasswordPrompts 2" -o "ServerAliveCountMax 1" -l root $machine $command
match_max 100000

expect {
    "assword:" 
      {
        exp_send $pass 
        set pass "xen!king\r"
        exp_continue
    }
}

First, the script has a password set as a variable. It allows to change later. To to this I have expanded the 'expect password' part of the script. Now the script sends the password and changes it after. If the password was fine, script executes the command. The change of the password is not important. If the password is wrong the script sends the variable $pass again, but this time it is new value. I have also added to option to ssh command for script to run a bit faster.

1. NumberOfPasswordPrompts 2 - ensure that ssh tries only twice to provide password.
2. ServerAliveCountMax 1 - ensure that ssh sends only one Server Alive message

Finally I have set StrictHostKeyChecking no and UserKnownHostsFile /dev/null in the .ssh/config file for machines I'm going to use above scripts. This two options set ssh not to bother about checking Host Key. Please remember that it might be not secure. 

Expect and operation on many computers

Recently, I had to delete a directory on around 200 computers. The directory belonged to root, so using my account with public key authentication wasn't possible. I googled a bit, found the expect and wrote the following script.

#!/usr/bin/expect -f

set machine [lindex $argv 0]
set command [lindex $argv 1]
set timeout -1
spawn ssh -l root $machine $command
match_max 100000

expect "?*assword: $"
send "password\n"

expect eof

The script sets the name of a remote machine (set machine [lindex $argv 0]) and a command (set command [lindex $argv 1]) to execute from arguments it is started with. Next tries to connect to the remote machine (spawn ssh -l root $machine $command) and when it's asked for the password (expect "?*assword: $") send it (send "password\n"). Of course you have to change the password to the root password. Finally, it waits for the EOF from ssh (expect eof). I have confess that I don't remember what exactly set timeout -1 and match_max 100000 means ;) The script can be called with loop similar to one below.

for cell in 1{0..3}{0..9} ;\
do for box in {1..4} ;\
do echo  c${bc}-box0${app} ; \
./command.script bc${bc}app-0${app} "ls /var/log/httpd" ; \
done; \
done

One more thing. The script assumes that you has connected at least one to all machines or rather that the machines has been added to your .ssh/know_hosts file. If you plan to use script to initialize the first connection you should add following line

expect "Are you sure you want to continue connecting (yes/no)?"
send "yes\n"

before the line expect "?*assword: $", but in such case all machine haven't to be present in .ssh/know_hosts file.