Awk study Note 6: awk mode and action

Each awk statement consists of a pattern and corresponding actions. The execution of the pattern control rule in the awk-a rule is executed when its pattern matches the current input record.
Special begin and end modes:
They provide awk ProgramStart and end actions,
The begin and end rules must have actions. They are executed only once in the program.
For example:
$ Awk 'in in {print "Analysis of \" foo \ ""}/Foo/{++ n} end {print "\" foo \ "appears", n, "Times. "} 'filename'
The begin rule prints the title, and the end rule prints the value of N.
An awk program can have multiple begin/end rules. They are executed in the order of appearance.

An action is composed of one or more awk statements starting with a pair of {} loops. Each statement performs one task. Each statement is separated by a new line or a comma.