Using I/O redirection
I/O redirection is one of the easiest things to master when it comes to the bash scripting. It's as simple as knowing where you want your input to go and where it's coming from. It may seem like this is a very interesting topic and you might not see why you need to know this, but redirecting output—if you truly get to understand what it's all about—will be what you're doing on your command line almost 80 percent of the time! It's essentially the one thing that allows you to combine different utilities and have them work together quite effectively on the command line in a compact and simple way. For instance, you may want to search through the output from
tcpdump or a key-logger by feeding its output to another file ...