Learning the shell. Why do you need to learn the command line anyway?
Well, let me tell you a story. Not long ago we had a problem where I used to work. Unix Shell Scripting Tutorial. We assign a local value to the variable value of 4.
The next three lines construct the the output we would like, remember that this is being echoed to some buffer and will be replace the function call with all the stuff that was passed to stdout within the function when the function exits. So the calling code will be replaced with whatever we direct to standard output within the function. Linux Shell Scripting Tutorial - A Beginner's handbook.