dpkg --get-selections | grep postgre

postgresql
postgresql-9.1
postgresql-client
postgresql-client-9.1
postgresql-client-common
postgresql-common
postgresql-contrib
postgresql-contrib-9.1
postgresql-server-dev-9.1
postgresql-server-dev-all
libpq-dev
libpq5

ERROR:  Error installing pg:
    ERROR: Failed to build gem native extension.

        /home/vedarthk/.rvm/rubies/ruby-1.9.3-p362/bin/ruby extconf.rb
checking for pg_config... yes
Using config values from /usr/bin/pg_config
checking for libpq-fe.h... yes
checking for libpq/libpq-fs.h... yes
checking for pg_config_manual.h... yes
checking for PQconnectdb() in -lpq... no
checking for PQconnectdb() in -llibpq... no
checking for PQconnectdb() in -lms/libpq... no
Can't find the PostgreSQL client library (libpq)

gem install pg -- --with-pg-include=/usr/include/postgresql/libpq --with-pg-lib=/usr/lib/postgresql/9.1/lib


gem install pg -- --with-pg-include=/usr/include/postgresql --with-pg-lib=/usr/lib/postgresql/9.1/lib