is the smallest decomposition unit that has its own value, and we will call it an elementary term. Basic terms can form the following terms:
Any number of white space characters (tab characters or spaces) between the operator and the base term There is no problem.
An expression means a string whose value can be evaluated.
Arbitrary expressions can be enclosed in parentheses, and the part enclosed in parentheses is one term. Are treated as
[A-F] [a-f] [0-9] ! # $ % & ( ) ? @
Some commands require an expression or an arbitrary string as an argument. A complete string of commands containing these necessary arguments is called a statement. The command name and argument must be separated by one or more white spaces, and the argument and argument must be separated by the character ',' (comma). There can be any number of white spaces before and after this comma.
Statement: command argument {, argument {, argument {, ...}}}