无法在Rails上安装pg gem
我试图捆绑安装，但是，由于一些奇怪的原因，pg gem在安装时返回以下错误：
$ gem install pg -v '0.18.4' Building native extensions. This could take a while... ERROR: Error installing pg: ERROR: Failed to build gem native extension. /Users/username/.rvm/rubies/ruby-2.2.1/bin/ruby -r ./siteconf20151221-23315-1tkv3fd.rb 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 --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/username/.rvm/rubies/ruby-2.2.1/bin/$(RUBY_BASE_NAME) --with-pg --without-pg --enable-windows-cross --disable-windows-cross --with-pg-config --without-pg-config --with-pg_config --without-pg_config --with-pg-dir --without-pg-dir --with-pg-include --without-pg-include=${pg-dir}/include --with-pg-lib --without-pg-lib=${pg-dir}/lib extconf failed, exit code 1 Gem files will remain installed in /Users/username/.rvm/gems/ruby-2.2.1/gems/pg-0.18.4 for inspection. Results logged to /Users/username/.rvm/gems/ruby-2.2.1/extensions/x86_64-darwin-15/2.2.0/pg-0.18.4/gem_make.out 任何人都可以帮我安装这个gem并使我的捆绑成功完成？
您需要正确配置pg。
跑：
bundle config build.pg --with-pg-config=/Applications/Postgres.app/Contents/Versions/(YOUR POSTGRES VERSION)/bin/pg_config
然后尝试运行bundle：
bundle install
您应该安装PostgreSQL开发库。
如果您使用的是Ubuntu，这将有助于：
sudo apt-get install libpq-dev
在Mac上：
brew install postgresql
如果安装了PostgreSQL客户端库，那么您需要告诉gem在哪里查找包含文件，它通过询问pg_config 。 我使用一个小shell文件使gem更容易找到该实用程序：
#!/bin/sh -x PATH=/Library/PostgreSQL/9.4/bin:$PATH gem install pg $@
您也可以手动调整PATH以始终包含PostgreSQL bin目录，该目录应永久修复问题。
如果升级PostgreSQL，该路径将发生变化，因此您可能需要重新安装pg和/或更改PATH设置。
一旦安装了pg，就可以在不重新运行脚本的情况下安装gem的进一步升级。