$ sudo apt-get install libx11-dev

Go to HTK download page. But first, need to register (free) At this time, HTK version is 3.5 beta(2). Download both HTK source code and HDcode page.

$ tar xzf HTK-3.5.beta-2.tar.gz
$ tar xzf HDecode-3.5.beta-1.tar.gz

Go to each of following folders: HTKLib, HLMLib, HTKTools, HLMTools, HTKLVRec and install like below:

$ cd HTKLib
$ make -f MakefileCPU all
$ make -f MakefileCPU install

(If you want to compile CPU using MKL or NVIDIA GPUs, change MakefileCPU according MakefileMKL, MakefileNVCC)

After run all install command, one directory is created under htk, named: bin.cpu. Need to set this directory as system-wide PATH. So, go to root directory and run:

$ sudo gedit /etc/environment

Add absolute path of bin.cpu directory in environment file and save it. Now, make change affect:

$ source /etc/environment

And check what we do is correct or not

$ echo $PATH

When Install HTK in step 2, there is also directory inside htk directory, named samples. If not, got to HTK download page to get it

$ cd samples
$ cd HTKDemo
$ mkdir -p hmms/{tmp,hmm.{0,1,2,3}} proto accs test
$ ./runDemo configs/monPlainM1S3.dcf

If test succeed, there is result like below:

--------------------- Overall Results -----------------------
SENT: %Correct=0.00 [H=0, S=3, N=3]
WORD: %Corr=63.91, Acc=59.40 [H=85, D=35, S=13, I=6, N=1
=============================================================