user8133: This page says to run a shell command I need a "proxy code" running on my computer (Linux Ubuntu). What do they mean by this, and how should I make one?

user220: I'm not familiar with the term proxy code, but I'm assuming that it's a piece of code on your computer that acts as a man in the middle.
You cannot directly use Arduino to run a shell command, so you'll need to create a program on your computer that listens to serial and then executes a command.
For the "proxy code" Python would be a good choice because of the pySerial library that plays nicely with Arduino. It seems fairly easy to execute a shell command with Python.
As per the Arduino code, something like this would work good:
setup() {
  Serial.begin(9600);
}

loop() {
  if(state == true) {
    Serial.print('A');
  }
}


8133: <p><a href="http://forum.arduino.cc/index.php?topic=38627.0" rel="nofollow">This page</a> says to run a shell command I need a "proxy code" running on my computer (Linux Ubuntu). What do they mean by this, and how should I make one?</p>
 220: <p>I'm not familiar with the term <em>proxy code,</em> but I'm assuming that it's a piece of code on your computer that acts as a man in the middle.</p>

<p>You cannot directly use Arduino to run a shell command, so you'll need to create a program on your computer that listens to <strong><a href="http://arduino.cc/en/reference/serial" rel="nofollow noreferrer">serial</a></strong> and then executes a command.</p>

<p>For the "proxy code" Python would be a good choice because of the <strong><a href="http://pyserial.sourceforge.net/" rel="nofollow noreferrer">pySerial library</a></strong> that plays nicely with Arduino. It seems <a href="https://stackoverflow.com/questions/89228/calling-an-external-command-in-python">fairly easy to execute a shell command with Python</a>.</p>

<p>As per the Arduino code, something like this would work good:</p>

<pre><code>setup() {
  Serial.begin(9600);
}

loop() {
  if(state == true) {
    Serial.print('A');
  }
}
</code></pre>
