RegEx: Regular Expressions

Regular Expressions (RegEx) are used to identify patterns of text.  This article is a basic introduction to RegEx and addresses common RegEx you might use in Angelfish.

RegEx is used throughout the entire Angelfish application to perform tasks like:

RegEx provides a flexible way to describe what the pattern looks like, using a combination of characters. 

Anchors match a specified pattern from the beginning or from the end of a field. The caret and dollar symbols are anchors.

The caret ^ matches a pattern from the beginning of the field. For example:

^/page/ matches the following:

The following patterns are not matched:

 

The dollar symbol $ matches a pattern to the end of the field. For example:

internal.corp$ matches the following:

The following patterns will not be matched:

You can combine anchors in a single pattern - here's an example of a match pattern for a specific Username:

RegEx is used to match individual characters, combinations of characters, and ranges of characters.

Brackets [] allow you to specify individual characters that appear in the string. Brackets look at each individual character, not whole strings.  

 

Rather than typing individual characters, you can type a range in a bracket. For example:

Parentheses () allow you to match a string of characters in a specific order, like (blue) and (green). 

To match multiple strings, enclose them in parentheses and use a pipe | between each string.

 

- Datasources

- Filters

- Report Search Field

 

With RegEx, you can specify the number of times a pattern should occur.

A question mark ? after a character matches zero or one of the previous item, which makes the item optional.

^crawl? matches the following:

(www\.)?website\.com$ matches the following

A plus sign + matches one or more of the previous item.

/+ matches the following slash patterns:

.+ is a wildcard that only matches a non-empty string

An asterisk * matches zero or more of the previous item.

.* is a wildcard that matches an empty or non-empty field.

Occasionally you'll want to match a character that has a RegEx value.  For example:

.com matches the following:

The backslash \ allows you to escape the value of a RegEx character. 

Using the above example, you can escape the RegEx value of the period by adding a backslash, like this:

\.com

This forces a match pattern of ".com" (dot com) instead of "any single character followed by com"

To match a series of special characters in a row, escape each character individually.

To match a single literal backslash, type two backslashes: the first backslash escapes the RegEx value of the second.

If you're unsure a character has a RegEx value or not, you can escape it with impunity.