title: Does anybody know where is LD_PRELOAD variable, in which file?
body: <p>
  Just as the title said, I don't know where does this variable locate. I just know how to change it by typing: 
  <code>$ export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libXpm.so.4</code>
  Then is it possible to change it in its file?
  </p>