[Chapter 7] 7.7 System Variables<

There are a number of system or built-in variables defined by awk. Awk has two types of system variables. The first type defines values whose default can be changed, such as the default field and record separators. The second type defines values that can be used in reports or processing, such as the number of fields found in the current record, the count of the current record, and others. These are updated by awk; for example, the current record number and input file name. There are a set of default values that affect the recognition of records and fields on input and their display on output. The system variable defines the field separator. By default, its value is a single space, which tells awk that any number of spaces and/or tabs separate fields. can also be set to any single character, or to a regular expression. Earlier, we changed the field separator to a comma in order to read a list of names and addresses. , which is a space by default. We'll see an example of redefining to be the number of fields for the current input record. Changing the value of actually has side effects. The interactions that occur when are changed is a murky area, particularly when is decreased.[7] Increasing it creates new (empty) fields, and rebuilds , with the fields