title: Writing a Shell script
body: <p>I'm trying to write a shell script that will essentially query a given condition. Here's the catch. I want it to repeat the query for a duration of 3 minutes. (probably run the query, and sleep for 2 seconds)</p>
  
  <p>After 1 minute, at any time IF the query returns null, the for loop will break. (the main objective is to DETECT if the query returns the results consistently for a duration of 3 minutes)</p>
  
  <p>How do I incorporate the checking for the BREAK statement in the below code, after 1 minute? (does SPOOL overwrite contents of files or does it append?)</p>
  
  <pre><code>for ((i=90; i &gt; 1 ; i--))
      do
      sqlplus -s username/passwd@SERVICENAME &lt;&lt;EOF
      SET PAGESIZE 50000
      SET TERM OFF
      SET HEAD OFF
      SET LINESIZE 200
      #SET TRIMSPOOL ON
      SET FEEDBACK OFF
  
      SPOOL /appl/odd/local/bin/notification_pending.txt
      select awb,rcvr_phone,rcvr_email,latest_event,latest_event_dtm,status,contact,notify_method from shipment t,notification t2 where t.id=t2.shp_id
      and t2.status like 'F%'
      and t2.contact not in ('Recipient not in whitelist','Invalid Email Id','Mail Service Down','Invalid Mobile Number');
  
      SPOOL OFF
      exit
      /
      EOF
      sleep 2
  done
  </code></pre>