Building control structures

…So far most of the AWK programs that we've seen are very simple, performing…a basic operation like printing each line or perhaps only some lines from its input.…But AWK is a full-fledged programming language with a full complement…of control structures to control the flow of execution through a program.…AWK's Control Structures are generally similar…to those of C programming language.…The if statement executes a block of code…if, and only if, a certain condition is true.…The condition is any expression that can have a true or false value.…Conditional operators like = =, which tests…for numerical string of quality, or ~ which…tests for regular expression matching, are true…if the condition is true and false otherwise.…

A numeric value is considered false if its value is…0 and true if its value is anything other than 0.…String values are considered false if…they're the empty string and true otherwise.…The braces around the if statements are optional, if there's only…one statement, but it's very good practice to use braces every time.…