Regular expressions

Regular expressions are used to recognize patterns with textual data. They evaluate text data and match an expression with the text in the document. In Kofax Transformation Modules, regular expressions are used in format locators, validation methods, and formatters, to identify and normalize items on a document.

Regular expressions describe data in an abstract way, and some common examples are listed in the following table:

Table 1. Regular Expression Syntax
Format Description Example Matches Does Not Match

C

One character

a

a

b,A

. (period)

Any character

b.g

bug, bag, big, bbg

bg, baag

\d

Any single digit

a\d

a5, a8, a0

aA, ab, a

c1c2c3

One character out of a set

[abc]

a, b, c

1, 2, d, D, A, ab, bc

[c1-cn]

One character out of a range

[a-z]

b, g, x

1, 2, D, A

? (question mark)

The previous term is optional

x\d?

x, x7, x1

xx, xq

+ (plus sign)

The previous term can be repeated one or more times

\d+

4, 2323, 100

A112, 2b, X

* (asterisk)

The previous term can be repeated zero or more times

x\d*

x6, x, x100

100x, xx

{n}

The previous term can be repeated exactly n times

y{3}

yyy

yy, yyyy

{m, n}

The previous term can be repeated between m and n times

\d{5,9}

12345, 999999999

1234, 999999999999

\

Escape special characters

\$ \\ \- \? \.

$ \ - ? .

!%

()

Group characters

a(\$\$)?b

a$$b, ab

a$b, a$$

(e1|e2)

Choice

(abc|ABC)

abc, ABC

aBC, AbC

\n

Back reference (nth item matched in round brackets needs to be matched again)

(\d)x\1

1x1,2x2,3x3,4x4...

1x2,6x7...

You can find many third-party resources on the internet about regular expressions. In many cases however, extensive knowledge of regular expressions is not needed because Kofax Transformation Modules provides a set of commonly used and predefined templates.

Note You can also use dictionaries in regular expressions for format locators. If you know the name of the dictionary, you can edit the input box of the format locator directly by typing the dictionary name as § + dictionary name + §. As there is no such symbol on the keyboard, you can generate this by typing Alt + 0167.

If any of your documents have special ASCII characters that you want to locate and extract, you can do so using regular expression codes for ASCII characters. The following table shows the conversion requirements.

ASCII Hex

Special Character

Regular Expression Code

21

!

\x21

22

"

\x22

23

#

\x23

24

$

\x24

25

%

\x25

26

&

\x26

27

'

\x27

28

(

\x28

29

)

\x29

2A

*

\x2A

2B

+

\x2B

5E

^

\x5E

A7

§

\xA7

For example, a single entry of \x2A can be used to match a single character. In this case, an asterisk (*). In addition, you can use these characters as a range. For example, [\x21-\x29] can locate any of the following characters; !"#$%&'().