Introduction of regular Expressions (Microsoft)--12. Locator

Locator character
Until now, the examples you see are only looking for chapter headings that appear anywhere. Any occurrence of a string ' Chapter ' followed by a space and a number may be a true chapter title, or it may be a cross-reference to other chapters. Because true chapter headings always appear at the beginning of a line, you need to design a method to find only the headings instead of looking for cross-references.
This feature is provided by the locator character. A locator can fix a regular expression at the beginning or end of a line. You can also create regular expressions that appear only within a word or only at the beginning or end of a word. The following table contains a list of regular expressions and their meanings:
Character description
^ matches the start position of the input string. If you set the Multiline property of the RegExp object,
^ also matches the position after ' or '.
$ matches the end position of the input string. If you set the Multiline property of the RegExp object,
$ also matches the position before ' or '.
Matches a word boundary, which is the position between the word and the space.
B matches a non word boundary.
Qualifiers cannot be used on the locator. An expression such as ' ^* ' is not allowed because there are no consecutive positions in front of or behind a newline character or word boundary.
To match the start of a line of text, use the ' ^ ' character at the beginning of the regular expression. Do not confuse the syntax of ' ^ ' with the syntax in the bracket expression. Their syntax is fundamentally different.
To match the text at the end of a line of text, use the ' $ ' character at the end of the regular expression.
To use a locator when finding chapter headings, the following Visual Basic scripting Edition Regular Expressions match the chapter headings at the beginning of a line with up to two digits:
/^chapter [1-9][0-9]{0,1}/
The regular expressions for the same functionality in VBScript are as follows:
"^chapter [1-9][0-9]{0,1}"
A true chapter title not only appears at the beginning of a line, but only in this line, so it must also be at the end of a line. The following expression ensures that the specified match matches only the chapter and does not match the cross-reference. It is accomplished by creating a regular expression that matches the start and end positions of only one line of text.
/^chapter [1-9][0-9]{0,1}$/
For VBScript use:
"^chapter [1-9][0-9]{0,1}$"
Matching word boundaries is a little different, but it adds a very important function to regular expressions. A word boundary is the position between a word and a space. A non word boundary is any other location. The following Visual Basic scripting Edition expression will match the first three characters of the word ' Chapter ' because they appear after the word boundary: