Execute command on remote machine using telnet in one line

Question

I need to write a script to monitor wlan0 interface of my remote machine. I can do this by executing iwconfig wlan0 repeatedly on remote machine. But how to login to that machine and execute this command via telnet. I can do this via ssh, but ssh takes time to login and it hangs if connection to remote machine drops in the middle of execution.

Answer 1

Instead of repeatedly invoking the ssh command, you could run ssh to repeatedly execute the command on the remote system and then parse and use the output locally. Then you wouldn't have to keep running the ssh connection and putting up with the initial lag.

For example:

ssh remotehost "while [ "1" ] ; do iwconfig wlan0 ; sleep 1 ; done"

Or, you could use netcat to send the output on the remote system back to your machine. For example, run this on the local machine:

nc -l 9999

Then on the remote machine:

while [ "1" ] ; do iwconfig wlan0 ; sleep 1 | nc localmachine 9999

Replace localmachine here with the host or ip of the machine that will be doing the "monitoring".

You could even pipe the output from nc reading that port into another command.

Closer to your actual question, you could do this on the remote system to act as a telnet "server":

while [ "1" ] ; do iwconfig wlan0 | nc -l 9999 ; done

Then you could do this to get the outupt:

telnet remotehost 9999