title: Match string with prefix and suffix use Logstash grok pattern
body: <p>I have a ELK cluster to keep my logs below, and i want to extract some fields in the log use logstash grok.</p>
  
  <pre><code>[info ][170703 10:34:38.998686/832]acct ok,deal_time=122ms;ACCESS_PORT=216179383538692472&amp;ACCESS_TYPE=2&amp;ACCOUNT=07592111916&amp;Acct-Status-Type=3;
  </code></pre>
  
  <p>here is my grok pattern.</p>
  
  <pre><code>%{SYSLOG5424SD}\[%{DATA:[@metadata][timestamp]}\/%{NUMBER}\]%{WORD:type}\ %{WORD:status}\,%{GREEDYDATA}%{NUMBER:dealtime}ms\;%{GREEDYDATA}(?&lt;acct&gt;(?&lt;=ACCOUNT=).*)
  </code></pre>
  
  <p>i want to extract some field's value and give it to the event variable.
  eg. acct = 07592111916</p>
  
  <p>i use (?(?&lt;=ACCOUNT=).*&amp;$) to extract the value, but not works, where is my problem?</p>
  
  <p>i debug the code in this site.
  <a href="http://grokdebug.herokuapp.com" rel="nofollow noreferrer">http://grokdebug.herokuapp.com</a></p>