All sources: How to use Transforms
How to Use Transforms
Example Config
yaml
sources:
  demo:
    type: file
    include: /home/me/demo_log_file.log
    sink: logscale
    transforms:
      # regex_filter transform can filter events by either including or excluding events matching a regex pattern.
      - type: regex_filter
        mode: include
        pattern: ^category=(error|warning|info|debug)

      # static_fields transform adds configured key, value pairs as fields
      - type: static_fields
        fields:
          mykey: myvalue
          #fields to add must be indented 2 spaces under the fields: label
          # Passing environment variables is supported
          myenvvar: $MY_ENV_VAR

You can use multiple events on one single line (recommended) or on multiple lines:

Single Line Transforms( AND or OR can be used in the regex statement) 

transforms:
  - type: regex_filter
    mode: exclude
    pattern: (some pattern|another pattern)

Multi-Line Transforms (the statements are treat as AND) 

transforms:
  - type: regex_filter
    mode: exclude
    pattern: some pattern

  - type: regex_filter
    mode: exclude
    pattern: another pattern