I'm using Postgres.app on OS X (10.8.3). I have modified my PATH so that the bin folder for the app is before all others.
Rammy:~ phrogz$ which pg_config
/Applications/Postgres.app/Contents/MacOS/bin/pg_config
I have rvm installed and can install the pg gem without error, but when I go to require it I get an error:
Rammy:~ phrogz$ gem -v
1.8.25
Rammy:~ phrogz$ gem install pg
Fetching: pg-0.15.1.gem (100%)
Building native extensions. This could take a while...
Successfully installed pg-0.15.1
1 gem installed
Rammy:~ phrogz$ ruby -v -e "require 'pg'"
ruby 1.9.3p392 (2013-02-22 revision 39386) [x86_64-darwin12.3.0]
/Users/phrogz/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': dlopen(/Users/phrogz/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.15.1/lib/pg_ext.bundle, 9): Library not loaded: @executable_path/../lib/libssl.1.0.0.dylib (LoadError)
Referenced from: /Applications/Postgres.app/Contents/MacOS/lib/libpq.dylib
Reason: image not found - /Users/phrogz/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.15.1/lib/pg_ext.bundle
from /Users/phrogz/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /Users/phrogz/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.15.1/lib/pg.rb:4:in `<top (required)>'
from /Users/phrogz/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:60:in `require'
from /Users/phrogz/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:60:in `rescue in require'
from /Users/phrogz/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:35:in `require'
from -e:1:in `<main>'
What do I need to do to get the pg gem properly installed?
This worked for me:
sudo env ARCHFLAGS="-arch x86_64" gem install pg -- --with-pg-config=/Applications/Postgres93.app/Contents/MacOS/bin/pg_config
Just double check that the /Applications/Postgres93.app.. path exists for you.