You may encounter the following errors if you try to run ./HTK_Compile_Model.sh on Ubuntu

==./HTK_Compile_Model.sh: 215: let: not found

If you are fast enough to press CTRL+C, you may also notice something like

-e     init

on the top.  This is because Ubuntu's sh command in /bin is mapped to /bin/dash instead of /bin/bash. Doing the following will sort out the issue

sudo rm /bin/sh

sudo  ln -s /bin/bash /bin/sh