title: subprocess in python not excecuting command
body: <p>I have a bit of code that I am designing to take a file, perform the dos2unix command on it, then copy that file to a file called INPUT, and then run a command that boots a program. From my code the first two tasks work flawlessly, however the script doesn't seem to excecute the command line which starts the program. However when I take the command line exactly as I have it written in the script, and pass it in terminal, it works fine. </p>
  
  <p>here is the code:</p>
  
  <pre><code>import subprocess
  
  import os
  
  os.chdir('/home/mike/testing/crystal')
  
  subprocess.Popen(['dos2unix mgo_input'], stdout=subprocess.PIPE, shell=True)
  
  
  subprocess.call(['cp mgo_input INPUT'], shell=True)
  
  
  subprocess.Popen(['mpirun -np 8 Pcrystal &lt;/dev/null &amp;&gt; mgo_singlepoint.out &amp;'], stdout=subprocess.PIPE, shell=True)
  </code></pre>
  
  <p>it is the mpirun section of the code that seems to be getting hung up</p>