error installing pg gem

gistfile1.txt

Installing pg (0.8.0) with native extensions /opt/local/lib/ruby/site_ruby/1.8/rubygems/installer.rb:482:in `build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

/opt/local/bin/ruby extconf.rb 
extconf.rb:1: command not found: pg_config --version
ERROR: can't find pg_config.
HINT: Make sure pg_config is in your PATH
*** 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=/opt/local/bin/ruby


Gem files will remain installed in /Users/heathertanner/.bundler/tmp/5188/gems/pg-0.8.0 for inspection.
Results logged to /Users/heathertanner/.bundler/tmp/5188/gems/pg-0.8.0/ext/gem_make.out
	from /opt/local/lib/ruby/site_ruby/1.8/rubygems/installer.rb:445:in `each'
	from /opt/local/lib/ruby/site_ruby/1.8/rubygems/installer.rb:445:in `build_extensions'
	from /opt/local/lib/ruby/site_ruby/1.8/rubygems/installer.rb:197:in `install'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/source.rb:100:in `install'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/installer.rb:55:in `run'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/spec_set.rb:12:in `each'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/spec_set.rb:12:in `each'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/installer.rb:44:in `run'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/installer.rb:8:in `install'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/cli.rb:217:in `install'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/vendor/thor/task.rb:22:in `send'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/vendor/thor/task.rb:22:in `run'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/vendor/thor/invocation.rb:118:in `invoke_task'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/vendor/thor.rb:246:in `dispatch'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/lib/bundler/vendor/thor/base.rb:389:in `start'
	from /opt/local/lib/ruby/gems/1.8/gems/bundler-1.0.0/bin/bundle:13
	from /opt/local/bin/bundle:19:in `load'
	from /opt/local/bin/bundle:19
captproton:osskids2 heathertanner$ sudo gem install pg
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
	ERROR: Failed to build gem native extension.

/opt/local/bin/ruby extconf.rb
checking for pg_config... no

  ===========   WARNING   ===========
  
  You are building this extension on OS X without setting the 
  ARCHFLAGS environment variable, and pg_config wasn't found in 
  your PATH. If you are seeing this message, that means that the 
  build will probably fail.

  If it does, you can correct this by either including the path 
  to 'pg_config' in your PATH or setting the environment variable 
  ARCHFLAGS to '-arch <arch>' before building.

  For example:
  (in bash) $ export PATH=/opt/local/lib/postgresql84/bin:$PATH                  
            $ export ARCHFLAGS='-arch x86_64'
  (in tcsh) % set path = ( /opt/local/lib/postgresql84/bin $PATH )
            % setenv ARCHFLAGS '-arch x86_64'

  Then try building again.

  ===================================
  
MacOS X build: fixing architecture flags:
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=/opt/local/bin/ruby
	--with-pg
	--without-pg
	--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
	--enable-static-build
	--disable-static-build


Gem files will remain installed in /opt/local/lib/ruby/gems/1.8/gems/pg-0.9.0 for inspection.
Results logged to /opt/local/lib/ruby/gems/1.8/gems/pg-0.9.0/ext/gem_make.out