title: How to create and extract new_field based on match [msg]
body: <p>hi all i use grok filtering and its all match. This part is ok. My concern is how to extract some data inside <code>%{GREEDYDATA:msg}</code> and create it as a field ?</p>
  
  <p>Example of <code>greddydata:msg</code> is like given below</p>
  
  <p>A B: C</p>
  
  <p>I used <code>%{WORD:a}</code> to test but unfortunately this tag just only able to read the A word and totally ignore B: C</p>
  
  <p>how to convert this A B: C to become one field ? 
  Any help is appreciated ! </p>