Build HTK in Ubuntu 16.04 with Minimum Effort

This post will walk through compilation of HTK on Ubuntu 16.04 64-bit. For macOS, take a look at this post.

First, you will need to download HTK from here. In this post, I will assume you download the latest stable version, 3.4.1. Extract the source files and change the directory
$ tar xfz HTK-3.4.1.tar.gz && cd htk

Because HTK was designed for 32-bit OS, we need to set the environment as such for 64-bit OS. Enter 32-bit environment by running
$ linux32 bash

Now, we do the usual things, starting off with configure
$ ./configure --prefix=$(pwd) && make

You will see an error:
HGraf.c:73:77: fatal error: X11/Xlib.h: No such file or directory
compilation terminated.

To find out which library you need, you can run the following
$ sudo apt-get install apt-file -y && apt-file update
$ apt-file search Xlib.h

You will see some lines of search result, one of which should read
libx11-dev: /usr/include/X11/Xlib.h

From this, you know that you need to install libx11-dev package.
$ sudo apt-get install libx11-dev -y

Let's resume make
$ make

You will encounter yet another error, complaining
Makefile:77: *** missing separator (did you mean TAB instead of 8 spaces?).  Stop.

It turns out that there is an error in HLMTools/Makefile line 77. In the very beginning of the line, there are a number of spaces, which should be replaced by a single tab.
<INSERT TAB HERE>if [ ! -d $(bindir) -a X_ = X_yes ] ; then mkdir -p $(bindir) ; fi

OK, let's continue.
$ make

You should see the compilation succeeds without any problem. Let's install this and you should find HTK binary files inside bin folder in the current directory!
$ make install
$ bin/HCopy