title: redirect output of bash script to all open terminals
body: <p><p>I'm trying to find a way to direct an echo command to all open terminals. Similar to the warning message sent out by "shutdown -k" that appears on all open terminals. Ideally I'd like more control over which users see the message then shutdown gives, but thats rather low on the priority list at the moment.</p>
  
  <p><p>The reason:<br>
  I'm tweaking a dynamic domain name update script (run in cron) that I made a few years ago. Currently the script writes its output to a log file for diagnostics and a conf file for its memory, now I want it to also display a message in open terminals when it recognises a new IP address.</p>
  
  <p><p>I know I've seen how to do this somewhere but I'm drawing a blank, and apparently failing at the googles.
  Thanks in advance for any replys.</p>