title: graphviz error: dot: can't open hello.dot (OSX El Capitan)
body: <p>I'm trying to install and use graphviz using Mac (El Capitan). As recommended on the graphviz website in the comments, I have installed xcode, xcode command tools, macports and updated macports. I have then installed graphviz via macports using the command </p>
  
  <p><strong>sudo port install graphviz-gui</strong></p>
  
  <p>I checked that graphviz installed correctly by typing</p>
  
  <p><strong>dot -h</strong></p>
  
  <p>in terminal, and got the response</p>
  
  <p><strong>$ dot -h</strong>
  <strong>dot: option -h unrecognized</strong></p>
  
  <p><strong>Usage: dot [-Vv?] [-(GNE)name=val] [-(KTlso)] </strong>
  <strong>...</strong> (etc.)</p>
  
  <p>indicating that the installation was successful.</p>
  
  <p>I then created two test files in text editor (named hello.dot and hello.gv).</p>
  
  <p>When I type</p>
  
  <p><strong>dot -Tpng -O hello.dot</strong></p>
  
  <p>in terminal, I get </p>
  
  <p><strong>Error: dot: can't open hello.dot</strong></p>
  
  <p>Same with hello.gv</p>
  
  <p>I have also tried opening hello.dot and hello.gv directly with graphviz.app but I get an error window pop-up that says "The document “hello.dot” could not be opened." or "The document “hello.gv” could not be opened."</p>
  
  <p>I have tried restarting terminal and restarting my computer, neither works.</p>
  
  <p>I have downloaded the .pkg installer for the latest version of graphviz, but am afraid to install it in case it interpheres with the macports-installed version of the app. Please can anyone advise if this is the case?</p>
  
  <p>I am <em>not</em> great with computers and this is my first time using terminal... so I'm really hoping that there is a really simple, silly thing that I'm doing wrong - I have watched every graphviz youtube tutorial and been through every help page I can find online, with no luck. I am at a loss - I can't figure out what is going wrong and would so appreciate some help - thanks in advance!</p>