Awk from getting started to being buried (2) understand the built-in variables and the use of variables in awk

Learning any language starts with variables .

Built in variable table

attribute	explain
$0	Current record （ As a single variable ）
$1$n	The current record number n A field , Between fields by FS Separate
FS	Enter field separator Default is space
NF	Number of fields in the current record , How many columns are there
NR	The number of records that have been read , It's the line number , from 1 Start
RS	Separator default of the entered record Consider line breaks \n
OFS	Output field separator The default is also a space
ORS	Record separator for output , The default is line break