Can't find the 'libpq-fe.h header when trying to install pg gem

Question

I am using the Ruby on Rails 3.1 pre version. I like to use PostgreSQL, but the problem is installing the pg gem. It gives me the following error:

Answer 1

I had also tried doing gem install libpq-dev, but I received this error:

Can't find the 'libpq-fe.h header
*** extconf.rb failed ***

However I found that installing with sudo apt-get (which I try to avoid using with Ruby on Rails) worked, i.e.

sudo apt-get install libpq-dev
# or
apt-get install postgres-server-dev-{pg.version}
# for postgresql 9.4 on Ubuntu 14.04

then I was able to do

gem install pg

without issues.