Cannot install the gem pg -v '0.15.1'

Question

I have tried installing the packet libpq-dev, and installing postgresql, but bundle install still fails due to gem pg. This is the error I get:

$ gem install pg -v '0.15.1'
Building native extensions.  This could take a while...
/.rvm/rubies/ruby-1.9.3-
p484/lib/ruby/site_ruby/1.9.1/rubygems/ext/builder.rb:73: warning: Insecure 
world writable dir /usr/local in PATH, mode 040777
ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

/.rvm/rubies/ruby-1.9.3-p484/bin/ruby extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again 
with --with-pg-config=/path/to/pg_config

checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** 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.

What is a proper way to clean up the mess?

Answer 1

If you are on Mac, install Homebrew and then install Postgres using the command

brew install postgresql

Or you can download and install Postgres from here depending on which OS you are using.

Answer 2

There isn't any "mess" - it's a standard issue where your system does not have the required libraries to install the gem

---

Library

As mentioned in the comments, you first need to install PGSQL, which will create the required library files to help the gem install, after that you can use some path references to help the gem install:

gem install pg -- --with-pg-dir="C:/Program Files/installer