Linux Shells by Example

5.6. Patterns and Actions

5.6.1. Patterns

Awk patterns control what actions awk will take on a line of input. A pattern consists of a regular expression, an expression resulting in a true or false condition, or a combination of these. The default action is to print each line where the expression results in a true condition. When reading a pattern expression, there is an implied if statement. When an if is implied, there can be no curly braces surrounding it. When the if is explicit, it becomes an action statement and the syntax is different. (See "Conditional Statements" on page 207.)

Example 5.23.

% cat employees Tom Jones 4424 5/12/66 543354 Mary Adams 5346 11/4/63 28765 Sally Chang 1654 7/22/54 650000 Billy Black 1683 9/23/44 336500 (The ...