运行 gem install pg -v '0.11.0' -- --with-pg-config=/usr/bin/pg_config 命令后的结果： （注，我已经 yum install 了 postgresql postgresql-server postresql-contrib）

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

/usr/local/bin/ruby extconf.rb --with-pg-config=/usr/bin/pg_config Using config values from /usr/bin/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 --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=/usr/local/bin/ruby --with-pg --without-pg --with-pg-dir --without-pg-dir --with-pg-include --without-pg-include=${pg-dir}/include --with-pg-lib --without-pg-lib=${pg-dir}/lib --with-pg-config

Gem files will remain installed in /usr/local/lib/ruby/gems/1.9.1/gems/pg-0.11.0 for inspection. Results logged to /usr/local/lib/ruby/gems/1.9.1/gems/pg-0.11.0/ext/gem_make.out