To understand the command syntax apply the following simple rules:
Any options or arguments enclosed in  square brackets are optional.
Anything not enclosed in  square brackets must be entered.
Boldface words are considered to be literals and must be typed exactly as they appear. This usually applies to the command name and command options.
Arguments shown in italics must be replaced by whatever it is that they represent. This is usually the name of a file or directory.
Ellipses '...' mean that the previous argument can be repeated any number of times.