title: Unable to create a directory using mkdir
body: <p>I installed Openfoam a couple of days ago . I could follow the instructions given <a href="http://www.openfoam.org/download/ubuntu.php" rel="nofollow noreferrer">here</a>
  without facing any major issues. However, when I run the command <code>$mkdir -p $FOAM_RUN</code> today, I am getting this error: <code>mkdir: missing operand</code>. I also tried <code>mkdir -p "$FOAM_RUN"</code> (it is suggested <a href="https://stackoverflow.com/questions/2743673/mkdir-error-in-bash-script/2743818#2743818">here</a>). Even this failed with the error message <code>mkdir: cannot create directory `': No such file or directory</code>. /.bashrc file is updated as per the instructions given on Openfoam website.</p>