Install GNU in Mac OS

If you don't know what's GNU, check here (http://www.gnu.org/gnu/gnu.html) and here (http://en.wikipedia.org/wiki/GNU).

Why Mac OS does not come with GNU? Here is what I extracted from Hong Xu's comment:

Because OS X is mainly BSD based -- the same reason why FreeBSD/OpenBSD/NetBSD does not use GNU tools by default. Another reason that Apple bundles many outdated GNU software (bash, gdb, etc.) is that the new GPLv3 doesn't allow Apple to do so, while GPLv2 is fine with this behavior. After many GNU projects upgraded to GPL v3, Apple won't be able to bundle them any more.

I found it's very easy to install GNU in Max OS just following Hong Xu's blog:
http://www.topbug.net/blog/2013/04/14/install-and-use-gnu-command-line-tools-in-mac-os-x/

Also recommend the friendly tool of Homebrew:
http://brew.sh/

Basically, here is step:

ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"

brew install coreutils  # contain most of what you want
brew install binutils 

brew install diffutils 

brew install ed --default-names 

brew install findutils --default-names 

brew install gawk 

brew install gnu-indent --default-names 

brew install gnu-sed --default-names 

brew install gnu-tar --default-names 

brew install gnu-which --default-names 

brew install gnutls --default-names 

brew install grep --default-names 

brew install gzip 

brew install screen 

brew install watch 

brew install wdiff --with-gettext 

brew install wget