Shell foundation
The first word entered in the command line must be the name of a command. The second word is the option or parameter of the command. Each word in the command line must be separated by spaces or TAB, the format is as follows: $ command option parameter option It is a code including one or more letters. It has a minus sign (the minus number is necessary. Linux is used to distinguish options and parameters), and the option can be used to change the type of action executed by the command. For example: [root @ start root] # ls This is an LS command without options, which can list all documents in the current directory, but only list the names of each document without displaying other more information. [root @ Start root] # ls -l
