Regular expressions and patterns in field normalization rules

Field Transformation definitions support the use of regular expressions (referred to in the platform as regex) and pattern matching for determining the position of characters in a string.

After identifying the target characters, field transformation can replace or delete the identified characters or insert other characters at that position.

Regex

Regular expressions can be used in transform parameters and in condition statements to determine which characters in a field value are transformed.

Regular expressions used as parameters to locate characters in transformed field values must begin with /regex/. Everything after that is a regular expression that is used to calculate character position.

Example

The computer names in an organization's Windows network are expressed as domain\machine name, such as development\devlab01. The network administrator wants to simplify these names by removing the domain name and backslash. He creates a transformation record for the Computer [cmdb_ci_computer] table and selects the Name field to transform.

Figure 1. Transformation regex example

The network contains several domains, and each domain contains numerous computers. The only character common to each name is the backslash. To delete the domain name, the administrator decides to use a regular expression to replace the entire raw value in the field with the characters that appear after the backslash (the actual machine name). He creates a new Transform using Replace as the Transform Type and enters the following values:

• Find:/regex/.*\\(.*)
• Replace with:$1

Figure 2. Transformation regex example

The regular expression .*\\(.*) represents the entire raw value in the Name field - in this example development\devlab01. The first part of the expression, .*, represents everything before the backslash (the development domain name). The backslash by itself is the escape character in regular expressions and requires special syntax to retain its function in the computer name. The administrator must escape it by using another backslash (\\ means \). The part of the expression after the backslash, (.*), represents the computer name (devlab01) and is grouped within parentheses for reference. The value in the Replace with field, $1, references this group and replaces the entire raw value of the field with the contents of the group, devlab01.

The administrator clicks Test transforms in the transformation record and enters development\devlab01 in the Raw data field. He then clicks OK to apply the transform to the test value. The transform replaces development\devlab01 with devlab01.

Figure 3. Transformation Regex 3

When the transforms for this field are tested successfully, the administrator changes the Mode in the transformation record to Active and runs the Transformation application data job to apply this transformation to existing records in the database.

• Pattern matching
  Pattern matching in Field Normalization uses special characters differently from regular expressions to create patterns that the platform recognizes when transforming field values.