title: Cannot execute command using exec() in php
body: <p>Ive tried searching for the answer but cant find anything proper in relation to my case.</p>
  
  <p>What i want to execute is very simple...its a call to the SPMF framework jar file.</p>
  
  <p>here is the code - </p>
  
  <pre><code>&lt;?php
  
  exec('java -jar spmf.jar run Apriori /opt/lampp/htdocs/rrugd/ip.txt /opt/lampp/htdocs/rrugd/output.txt %20');
  ?&gt;
  </code></pre>
  
  <p>why is this not executing?
  it obviously runs perfectly using cli.
  the folder having all the files (jar file,ip.txt,output.txt) have permissions set to r/w to all users</p>
  
  <p>I am on Linux - Ubuntu 13.10</p>