Trouble running 'rails s' after installing OS X Mavericks

Question

After installing OS X Mavericks, I cannot get an old Rails 4 app to work. The main issue seems to be trouble installing the pg gem:

Christophers-MacBook-Pro-2:DataSquid christopherspears$ gem install pg -v '0.17.1'
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
Christophers-MacBook-Pro-2:DataSquid christopherspears$ sudo gem install pg -v '0.17.1'
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/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.

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=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
    --with-pg
    --without-pg
    --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}/


Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/pg-0.17.1 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/gems/pg-0.17.1/ext/gem_make.out

I am not sure what the issue is. I did install the command line tools for OS X Mavericks for Xcode (late October 2013), but that did not resolve the issue.

Answer 1

As this question recommends, the easiest way is to install Postgres.app and then run

gem install pg -- --with-pg-config=/Applications/Postgres.app/Contents/Versions/9.3/bin/pg_config

to install the pg gem using the Postgres.app pg_config .