Can't install rails on OSX El Capitan? - ruby-on-rails

Question

Using installrails.com to install rails and everything works fine until I get to the first step:
gem install rails --no-ri --no-rdoc
After typing this, the terminal outputs:
users-MacBook:~ user$ gem install rails --no-ri --no-rdoc
Building native extensions. This could take a while...
ERROR: Error installing rails:
ERROR: Failed to build gem native extension.
/Users/user/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20151102- 1332-1uwdkth.rb extconf.rb
checking if the C compiler accepts ... yes
checking if the C compiler accepts -Wno-error=unused-command-line- argument-hard-error-in-future... no
Building nokogiri using packaged libraries.
-----
The file "/usr/include/iconv.h" is missing in your build environment,
which means you haven't installed Xcode Command Line Tools properly.
To install Command Line Tools, try running `xcode-select --install` on
terminal and follow the instructions. If it fails, open Xcode.app,
select from the menu "Xcode" - "Open Developer Tool" - "More Developer
Tools" to open the developer site, download the installer for your OS
version and run it.
-----
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers. Check the mkmf.log file for more details. You may
need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/Users/user/.rvm/rubies/ruby-2.2.1/bin/$(RUBY_BASE_NAME)
--help
--clean
--use-system-libraries
--enable-static
--disable-static
--with-zlib-dir
--without-zlib-dir
--with-zlib-include
--without-zlib-include=${zlib-dir}/include
--with-zlib-lib
--without-zlib-lib=${zlib-dir}/lib
--enable-cross-build
--disable-cross-build
extconf failed, exit code 1
Gem files will remain installed in /Users/user/.rvm/gems/ruby- 2.2.1/gems/nokogiri-1.6.6.2 for inspection.
Results logged to /Users/user/.rvm/gems/ruby-2.2.1/extensions/x86_64-darwin-14/2.2.0-static/nokogiri-1.6.6.2/gem_make.out
users-MacBook:~ user$
After some research I found I may be able to fix it by installing the Xcode command line tools, but I need further help.

Answer 1

The error message tells you exactly what went wrong:
The file "/usr/include/iconv.h" is missing in your build environment,
which means you haven't installed Xcode Command Line Tools properly.
And how to fix the problem:
To install Command Line Tools, try running xcode-select --install on
terminal and follow the instructions. If it fails, open Xcode.app,
select from the menu "Xcode" - "Open Developer Tool" - "More Developer
Tools" to open the developer site, download the installer for your OS
version and run it.
Please check:
Do you have Xcode installed?
Do you have the Xcode Command Line Tools installed?
Did you open Xcode at least once (and again after every update) and did you accept the licence?