Editing pattern

In [[awk]], patterns are used to select lines of input for processing. The pattern within each [[rule]] describes a section within a line of text that needs to be matched, in order for the associated [[action]] to take place. The [[action]] only executes if its relevant pattern was matched or the pattern was omitted from the [[rule]]. === Regular Expression Patterns === A pattern may contain [[regular expression]]s for matching text within a string. The [[slash]] symbol is used as an [[enclosure]] for [[regular expression]]s used in the pattern. In the following example, the [[action]] (to print the line) will occur for each line that match the [[regular expression]] foobar. {{{ /foobar/ {print $0} }}} === Start and End Patterns === It is possible to create a pattern consisting of two [[regular expression]]s separated by a [[comma]] symbol to mark start and ending points for text selection. The following will select all [[record]]s between [[foo]] and [[bar]]: /foo/,/bar/ ==== The two patterns must be in separate records ==== Note that [[foo]] selects the first matching [[record]], [[bar]] must be in a later [[record]]. If a single record containing both [[foo]] and [[bar]] is matched, then the [[record]] will be selected, but subsequent [[records]] will also be selected, because [[awk]] will continue to look for the ending pattern [[bar]]. === Boolean Patterns === The [[action]]within a [[rule]] will take place, if the [[expression]] within the pattern evaluates to [[true]]: {{{ 0 {print "Hello"} # This will not cause output, because a value of zero is considered to be false 1 {print "Goodbye"} # This will cause output, because a value of one is considered to be true }}} === Omission of the pattern === If a [[rule]] does not include a pattern, then the [[action]] within the [[rule]] is performed for every [[input]] line.

Summary:

This change is a minor edit.

Username: