Can't install pg gem on Rails

Question

I am trying to bundle install, but, for some strange reason, the pg gem is returning the following error on install:

$ gem install pg -v '0.18.4'
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

    /Users/username/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20151221-23315-1tkv3fd.rb 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.

Provided configuration options:
    --with-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/username/.rvm/rubies/ruby-2.2.1/bin/$(RUBY_BASE_NAME)
    --with-pg
    --without-pg
    --enable-windows-cross
    --disable-windows-cross
    --with-pg-config
    --without-pg-config
    --with-pg_config
    --without-pg_config
    --with-pg-dir
    --without-pg-dir
    --with-pg-include
    --without-pg-include=${pg-dir}/include
    --with-pg-lib
    --without-pg-lib=${pg-dir}/lib

extconf failed, exit code 1

Gem files will remain installed in /Users/username/.rvm/gems/ruby-2.2.1/gems/pg-0.18.4 for inspection.
Results logged to /Users/username/.rvm/gems/ruby-2.2.1/extensions/x86_64-darwin-15/2.2.0/pg-0.18.4/gem_make.out

Can anyone please help me install this gem and make my bundle finish successfully?

Answer 1

You should probably install the PostgreSQL development libraries.

If you're on Ubuntu this will help:

sudo apt-get install libpq-dev

On a Mac:

brew install postgresql

Answer 2

You need to configure pg correctly.

Run:

bundle config build.pg --with-pg-config=/Applications/Postgres.app/Contents/Versions/(YOUR POSTGRES VERSION)/bin/pg_config

Then try to run bundle:

bundle install