I have an Actiontec linux-based modem/router. The default configuration for this router saves the last fifty-so host names that anyone on your network looked up. This is cool but not something that I normally use or prefer to have. So I looked up instructions on disabling this feature on this site. The only problem was that since /var is mapped to the RAM, my changes would get reset every time I restarted the modem. Me being the type of person that I am, had to come up with a way to automate this.
The router uses BusyBox shell and allows you to telnet in. First I tried creating a bash script to automate the task but that didn’t work because telnet was expecting the input from the tty instead of a pipe. So I started exploring my options and found expect. expect is an awesome utility created for exactly this purpose, automating interactive applications. I ended up spending a little bit more time on learning the basic syntax (very few commands), and then went on to write the following expect script. This script telnets to the server, deletes the /var/tmp/log_web_activity and links it to /dev/'.
#!/usr/bin/expect -f spawn telnet 192.168.6.1 expect "login:" send "admin\n" expect "Password: " send "REPLACE_WITH_YOUR_PASSWORD\n" expect "# " send "cd /var/tmp;ls -ld log_web_activity\n" expect "# " send "rm log_web_activity\n" expect "# " send "ln -s /dev/' log_web_activity;ls -ld log_web_activity\n" expect "# " send "logout" puts "\n----- Finished -----"
If you have not explored expect yet then I would definitely suggest spending some time on it. It is a pretty good tool to have in your arsenal.