FILTER Functional Keyword

Feature	Since Version	Notes
`FILTER`	>v1.6.0	Data filtering using regex patterns

Overview

Description: Filters data from the payload or other sources using regular expressions (regex). Useful for extracting specific patterns or substrings from complex data streams.

Signature

Syntax:

FILTER <source> USING REGEX "<regex_pattern>"

Parameters

<source>: The data source to filter. Typically PAYLOAD, GET TOPIC result, or a {variable}.
<regex_pattern>: A regular expression pattern that defines what data to extract.

Usage Examples

Basic Example

Extract numeric values following a specific marker:

DEFINE ACTION FilterNumericAfterB1
ON TOPIC "MachineData" DO
    PUBLISH TOPIC "FilteredData" WITH FILTER PAYLOAD USING REGEX "(?<=B1;)(.*?)(?=B2)"

Explanation: - (?<=B1;): Lookbehind - matches text that follows B1; - (.*?): Captures any characters (non-greedy) - (?=B2): Lookahead - stops at B2

Intermediate Example

Filter sensor data from complex payload:

DEFINE ACTION ExtractTemperature
ON TOPIC "sensors/raw_data" DO
    SET "temp_data" WITH FILTER PAYLOAD USING REGEX "temp:(\d+\.\d+)"
    PUBLISH TOPIC "sensors/temperature" WITH {temp_data}

Advanced Example

Extract multiple fields using regex:

DEFINE ACTION ParsePLCData
ON TOPIC "plc/raw" DO
    SET "numeric_values" WITH FILTER PAYLOAD USING REGEX "(?<=B1;)(-?\d+(\.\d+)?;)+"
    PUBLISH TOPIC "plc/filtered" WITH {numeric_values}

Regex Pattern Examples

Pattern	Description	Example Match
`\d+`	One or more digits	`123`
`\d+\.\d+`	Decimal number	`45.67`
`-?\d+`	Optional negative sign with digits	`-123` or `456`
`(?<=prefix).*`	Text after prefix	Text following `prefix`
`.*(?=suffix)`	Text before suffix	Text before `suffix`

Notes & Additional Information

Regex patterns follow standard regex syntax
Use lookahead (?=) and lookbehind (?<=) for context-based extraction
Non-greedy matching .*? prevents over-capturing
Test regex patterns before deployment to ensure correct matching