UNIX command lines can be as simple, one-word entries like
pwd
or complex sentences like:
ls –R list.txt
UNIX commands may or may not contain arguments. An argument is an option or a filename. A UNIX command is written as:
command option(s) filename(s)
Options modify the way a command functions. For example, ls would simply print the directory listing. ls –al would give a listing with file details.
UNIX has a lot of commands. UNIX command line software such as vi editors also comes with its own set of commands. Attempting to memorize all the commands and their various options would be a waste of time. Instead, you should learn the commands and their options as you use them.
Every now and then, you would come across a frozen terminal. In such cases, try hitting the return key, ctrl-Q, ctrl-D or ctrl-Z.