为Heroku安装PostgreSQL gem pq
这里的第一个问题，但我现在非常感谢你，因为stackoverflow在michael hartl tut的第一章中帮了我近15次。
现在我正在尝试使用此命令安装PostgreSQL（pg gem）：
`
group :production do gem 'pg', '0.15.1' gem 'rails_12factor', '0.0.2' end` 但它显示出错误
-bash: group: command not found
然后我尝试直接安装（？）gem
gem install pg
但它显示了另一个错误
`Fetching: pg-0.17.1.gem (100%) Building native extensions. This could take a while... ERROR: Error installing pg: ERROR: Failed to build gem native extension. rvm/rubies/ruby-2.0.0-p353/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=/Users/trabalho/.rvm/rubies/ruby-2.0.0-p353/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}/ extconf failed, exit code 1 Gem files will remain installed in .rvm/gems/ruby-2.0.0-p353@railstutorial_rails_4_0/gems/pg-0.17.1 for inspection. Results logged to .rvm/gems/ruby-2.0.0-p353@railstutorial_rails_4_0/extensions/x86_64-darwin-10/2.0.0/pg-0.17.1/gem_make.out`
我无法理解它是否安装，我怎么能确认。 如何使组命令工作？ 或者我如何安装gem pg和rails_12factor？ 有帮助吗？
你在运行ubuntu吗？ 看起来你需要这个库：
sudo apt-get install libpq-dev
资源
您不希望从终端运行group ...作为命令，而是将该代码块放在rails应用程序的Gemfile中。
的Gemfile
group :production do gem 'pg', '0.15.1' gem 'rails_12factor', '0.0.2' end
然后运行bundle命令。
如果您仍然无法以这种方式编译pg gem，那么您需要确保安装了xcode命令行工具（假设您使用的是OSX）。 要安装这些，只需从终端运行xcode-select --install并按照提示操作即可。
sudo apt-get install libpq-dev
它帮助我在Ubuntu上