How can I cd to an alias directory in the Mac OSX terminal

you can make symbolic link to it.

ln -s EXISTING_PATH LINK_NAME

e.g.

ln -s ~/Documents/books ~/Desktop/

Reference

Enter into a directory through an alias in Mac OS X terminal

I personally use this to quickly work in the directory which is present deep inside one of my Volumes in my Mac.

Open your ~/.bash_profile, create an alias to the directory by adding this:

alias cdh="cd /Volumes/Haiku/haiku/src/apps/superprefs"

Save it, restart your terminal. Now on typing cdh in your terminal should change the working directory to the one mentioned as the alias.

All i want is to open my terminal and type cd htdocs so that i can work from there.

The easier approach is probably to ignore the links and add the parent directory of your htdocs directory to the CDPATH environment variable. bash(1) will check the contents of the CDPATH environment variable when you type cd foo to find the foo directory in one of the directories listed. This will work no matter what your current working directory is, and it'll be easier than setting symbolic links.

If the path to your htdocs is located /srv/www/htdocs/, then you could use CDPATH=/srv/www. Then, cd foo would first look for /srv/www/foo/ and change to it if it exists; if not, then it would look for foo in the current working directory and change to it if it exists. (This might get confusing if you have multiple htdocs directories on your system; in that case, CDPATH=.:/srv/www would let you change into a child directory easily but still use the /srv/www/htdocs/ version if no ./htdocs directory is present.)

You can add the CDPATH=/srv/www line to your ~/.bashrc file so it works every time you start a terminal.

I am not sure how OSX exposes Alias links but since you are using bash you can just create a variable in your .bashrc file.

On its own line put:

htdocs=YourDirectoryPath/

Once you have restarted bash you can just type cd $htdocs