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Examples of Screening Rules

This section provides examples of screening rules.

Credit Card Number

To find text that includes a typical credit card number, you need to match a sequence of four groups of four digits, each group separated by -(hyphen):

This regular expression also works without the \ (backslash) before the hyphens. However, it is better practice to write \- for the character hyphen, because the hyphen also has a special use in range expressions like [a-z].

Or if you want to allow for the possibility that some people will omit the hyphens, use? to make the hyphen optional:


You could also use the repetition notation to shorten each \d\d\d\d to \d{4}.

North American Phone Number

North American phone numbers consists of ten digits, grouped into two groups of three and one of four. There are a number of ways for the groups to be separated:

      (203) 555-1234
      203 555-1234

The following regular expression matches all of the above:


The table "Phone Number Regular Expression" analyzes this regular expression.

Phone Number Regular Expression





Three digits


Three digits, or three digits enclosed in parentheses

\ turns off the special meaning of the character (


Space or period or hyphen or zero

Any one of the items enclosed in square brackets, either once or not at all


Zero or more spaces


Three digits


Hyphen or period

Note again the need to use \


Four digits

Telltale Words

To screen for interactions from dissatisfied customers, you might try a regular expression like the following:

      (not\s([a-z]+\s)*(pleased | satisfied)) | unhappy | complain

The first part of this expression matches not followed by zero or more words followed by pleased or satisfied; for example, not very pleased, not satisfied, not at all satisfied (but it also matches strings like can not believe how pleased I am). The rest matches the single words "unhappy" and "complain."

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This page was last modified on 10 August 2017, at 06:39.