The subpatterns of a boolean pattern can be constant regular expressions, comparisons, or any other gawk expressions. Range patterns are not expressions, so they cannot appear inside boolean patterns. Expressions as Patterns Any awk expression is valid also as a pattern in gawk . The expression is reevaluated each time the rule is tested against a new input record. Comparison patterns are actually a special case of this.
Boolean patterns are also special cases of expression patterns.
A constant regexp as a pattern is also a special case of an expression pattern. A range pattern is made of two patterns separated by a comma, of the form begpat , endpat . It matches ranges of consecutive input records. The first pattern begpat controls where the range begins, and the second one endpat controls where it ends. The range pattern matches this record.