# Generate from pattern
This function generates a value based on a user-defined pattern.
This function is applied only on Strings.
| Option | Description |
| --- | --- |
| Extra parameter | This function requires an extra parameter.
The extra parameter is a pattern that
follows those rules:
- A is replaced with a random Latin uppercase letter.
- a is replaced with a random Latin lowercase letter.
- 9 is replaced with a random digit.
- H is replaced with a random Hiragana character.
- K is replaced with a random full-width Katakana character.
- k is replaced with a random half-width Katakana character.
- C is replaced with a random Kanji character.
- G is replaced with a random Hangul character.
All other characters are copied to the generated value
as is.
For more information about the supported
character types and the related Unicode ranges, see [Data masking functions in the masking components](https://help.qlik.com/talend/en-US/components/7.3/data-privacy/data-masking-functions-in-masking-components).
You can also use
numbered backreferences (\\<number>) using the following syntax: <pattern>\\<number>,<group1>,<groupN>.
- <pattern> corresponds to the pattern to be used for generating the output value.
- \\<number> is a numbered backreference. <number> identifies the position of the group placed after the "," character.
- <group1>,<groupN> are comma-separated groups of characters. Each group is treated as a single unit. If a backreference calls a group, it is added as is in the generated value.
If you want to copy a character used in patterns
(A, a,
9, H,
h, K,
k, C,
G) as is in the generated value, use a
backreference. |
This function does not work correctly if a comma ',' is used in the pattern.
In the following example:
* a characters are replaced with random Latin lowercase letters.
* s characters are not masked in the generated output.
* \\2 calls the group placed after the second "," character, which is @talend.com.
| Input value | Extra parameter | Example of a masked value |
| --- | --- | --- |
| A26 | "aaaass\\2,@gmail.com,@talend.com" | hjdfss@talend.com |
In the following example:
* \\3 calls the group placed after the third "," character, which is a.
* 9 characters are masked with random digits.
| Input value | Extra parameter | Example of a masked value |
| --- | --- | --- |
| A26 | "\\39999,D,Z,a" | a4825 |