title: Meaning of OPEN(..., SHARED) in Fortran
body: <p>I'm porting a legacy Fortran console app to C# and encountered this statement:</p>
  
  <pre><code>    OPEN(UNIT=12,FILE = bufProgress,STATUS='UNKNOWN'
      1 ,SHARED,ERR = 9300)
  </code></pre>
  
  <p>(Indentation as-is.) What does <code>SHARED</code> mean in this context? (And it is part of the <code>OPEN</code> statement due to the <code>1</code> used for line continuation, right?)</p>
  
  <p>Things I've found:</p>
  
  <ul>
  <li>There are no variables with this name in the entire program (comprising a single +7k-line file).</li>
  <li>This program was at one time compiled with "Digital Visual Fortran 6.0 Professional", a couple decades ago. I believe Intel's Fortran compiler has been used in the past decade, but am not sure.</li>
  <li>The file specified by the contents of buffer is (when the program is running as part of its "parent" multi-platform system) being written to by this console app and read from by another process.</li>
  <li><p>There is a commented-out statement just above this statement that looks like this:</p>
  
  <pre><code>c   OPEN(UNIT=12,FILE='progress.tmp',STATUS='UNKNOWN'
  c   1 ,SHARE='DENYRD',ERR = 9300)
  </code></pre>
  
  <p>It seems like <code>SHARE='DENYRD'</code> once had a similar semantic at one point?</p></li>
  <li>I've found nothing online regarding <code>SHARED</code> or <code>SHARE</code> in the context of <code>OPEN</code>.</li>
  </ul>