user34933: I have a Uno program and I can transfer data to Processing using println. In Processing bufferUntil('\n') interprets the ln  as \n, stops buffering, and reads the string until the next '\n'. I would like to use something other than ln to trigger Processing. That way I can use Serial Monitor in the Uno to see serial data when Processing is not running at the same time.
I have searched the net but have not found the technique to use something other than ln. Thanks.

user8561: If I understand your question (which is not certain):

Pick a different "trigger" byte that you won't be sending in your messages.  Maybe TAB?
In your "Processing" program, use: port.bufferUntil(TRIGGER);
In your Arduino sketch, rather than println, use print to send both your data and the trigger byte:  Serial.print(your_message); Serial.print(TRIGGER);

Note that sending binary data will cause this to fail when the data uses the trigger byte.
From: https://www.arduino.cc/en/Serial/Println The println()
   method sends your output then a CR and NL.  And it seems bufferUntil() takes a character on which to trigger:
https://processing.org/reference/libraries/serial/Serial_bufferUntil_.html

34933: <p>I have a Uno program and I can transfer data to Processing using println. In Processing bufferUntil('\n') interprets the ln  as \n, stops buffering, and reads the string until the next '\n'. I would like to use something other than ln to trigger Processing. That way I can use Serial Monitor in the Uno to see serial data when Processing is not running at the same time.</p>

<p>I have searched the net but have not found the technique to use something other than ln. Thanks.</p>
 8561: <p>If I understand your question (which is not certain):</p>

<ul>
<li>Pick a different "trigger" byte that you won't be sending in your messages.  Maybe <em>TAB</em>?</li>
<li>In your "Processing" program, use: <code>port.bufferUntil(TRIGGER);</code></li>
<li>In your Arduino sketch, rather than <em>println</em>, use <em>print</em> to send both your data and the trigger byte:  <code>Serial.print(your_message); Serial.print(TRIGGER);</code></li>
</ul>

<p>Note that sending binary data will cause this to fail when the data uses the trigger byte.</p>

<p><em>From: <a href="https://www.arduino.cc/en/Serial/Println" rel="nofollow noreferrer">https://www.arduino.cc/en/Serial/Println</a> The <strong>println()</strong>
   method sends your output then a CR and NL.  And it seems <strong>bufferUntil()</strong> takes a character on which to trigger:
<a href="https://processing.org/reference/libraries/serial/Serial_bufferUntil_.html" rel="nofollow noreferrer">https://processing.org/reference/libraries/serial/Serial_bufferUntil_.html</a></em></p>
