gem install pg | Can‘t find the ‘libpq-fe.h header

gem install pg
Building native extensions.  This could take a while…
ERROR:  Error installing pg:
        ERROR: Failed to build gem native extension.

/home/kahwee/.rvm/rubies/ruby-1.9.2-head/bin/ruby extconf.rb
checking for pg_config… no
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=/home/kahwee/.rvm/rubies/ruby-1.9.2-head/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 /home/kahwee/.rvm/gems/ruby-1.9.2-head/gems/pg-0.9.0 for inspection.
Results logged to /home/kahwee/.rvm/gems/ruby-1.9.2-head/gems/pg-0.9.0/ext/gem_make.out

so you must run sudo apt-get install libpq-dev first

then gem install gem install pg

then you can find success