Here are examples of using regular expressions to extract matching text in automation scripting.

Matching a single capture group

The pattern is a KATA key.

start:
  set:
    text: Your Amazon Order #Z-1234-5678-9 has shipped!
    pattern: /Amazon Order #([A-Z0-9\-]+)/
  return:
    order_id: {{text|regexp(pattern, 1)}}

We're taking the value of the text placeholder and applying a |regexp filter to it. That filter expects its first argument to be a regular expression pattern, and the optional second argument is a specific capture group to return (opposed to all matches as an array).

In the first argument, we're giving the pattern /Amazon Order #([A-Z0-9\-]+)/:

• / is the pattern delimiter, in the format of /<pattern>/<flags>.
• Amazon Order # matches text that starts with that phrase.
• (...) is a "capture group" for text after the previous match. Capture groups are defined with parentheses and you can have many of them. They can also be nested like ((\d)-(\w+)), in which case they're numbered from the left-most opening parenthesis (.
• [A-Z0-9\-]+ matches one or more consecutive characters while they are capital letters, digits, or a dash (-). The [...] brackets list the characters to match. The + at the end means "one or more", opposed to * which would mean "zero or more'.

Setting the pattern as a variable

The pattern is a scripting variable.

start:
  set:
    mask@text:
      {% set text = "The ticket mask that I am looking for is: KRN-69622-357 something else" %}
      {% set pattern %}/[A-Z]{3}-\d{5}-\d{3}/{% endset %}
      {{text|regexp(pattern)}}
  
  outcome/hasMask:
    if@bool: {{mask}}
    then:
      return:
        output: The ticket mask is #: {{mask}}

Using multiple capture groups

The second argument to |regexp specifies the capture group to return.

start:
  set:
    text: (123,456)
    pattern: /^\((\d+),(\d+)\)$/
  return:
    x@int: {{text|regexp(pattern, 1)}}
    y@int: {{text|regexp(pattern, 2)}}

Returning all matches for all capture groups

Use the regexp_match_all() function to return multiple capture groups for all matches.

• automation
• output

• start:
    set:
      headers@text:
        X-Mailer: Cerb
        From: customer@cerb.example
        To: support@cerb.example
    return:
      results@text:
        {% set results = regexp_match_all("#^(.*?): (.*?)$#m", headers) %}
        {{results|json_encode|json_pretty}}

• __return:
    results: |-
      [
          [
              "X-Mailer: Cerb",
              "From: customer@cerb.example",
              "To: support@cerb.example"
          ],
          [
              "X-Mailer",
              "From",
              "To"
          ],
          [
              "Cerb",
              "customer@cerb.example",
              "support@cerb.example"
          ]
      ]