Automate Multi-Server Commands with Expect: A Quick Guide

Recently, through the book "exploring expect", I learned the Expect scripting language, an extension of Tcl, used to solve automation problems where tools cannot interact automatically, such as providing a password during SSH login.

#!/usr/bin/expect
#purpose:auto run command on multiple servers
#how to:  mms <user> <cmd>
#write by zhumaohai.
#blog:http://www.centos.bz/
if {$argc < 2} {
    puts "usage: mms <user> <cmd>"
    exit 1
}
#set servers
set SERVERS {"192.168.0.100" "192.168.0.101" "192.168.0.102"}
#set password
set PASSWORDS(user1) "passwd1"
set PASSWORDS(user2) "passwd2"
#get variables
set USER [lindex $argv 0]
set CMD [lrange $argv 1 end]
set passwd $PASSWORDS($USER)
foreach x $SERVERS {
    eval spawn ssh -l $USER $x $CMD
    expect {
        "password" { send "$passwd\r" }
        "yes/no" { send "yes\r"; exp_continue; }
    }
    expect eof
}

The script defines three servers (192.168.0.100, 192.168.0.101, 192.168.0.102) and passwords for users user1 and user2; save the script as ms and run it as ./ms user1 date to execute the date command on all servers. Ensure the expect package is installed (e.g., yum install expect on CentOS or apt-get install expect on Ubuntu).