Create batch_cmd.sh

A shell script that can execute the same command in several servers once
how to use：
1. save the shell as batch_cmd.sh and "chmod a+x batch_cmd.sh" to make it executable
2. write a list of servers' addresses to a file line by line , e.g name server_list 
3. execute command like this:   batch_cmd.sh server_list  'rm /home/nuaazdh/old.log'  to remove the file old.log at /home/nuaazd  in every server