gem install pg -v '0.18.2'Building native extensions.  This could take a while...ERROR:  Error installing pg:    ERROR: Failed to build gem native extension.    current directory: /Users/bevan/.rvm/gems/ruby-2.3.0/gems/pg-0.18.2/ext/Users/bevan/.rvm/rubies/ruby-2.3.0/bin/ruby -r ./siteconf20160226-49308-30rbgs.rb extconf.rbchecking for pg_config... noNo pg_config... trying anyway. If building fails, please try again with --with-pg-config=/path/to/pg_configchecking for libpq-fe.h... noCan't find the 'libpq-fe.h header*** extconf.rb failed ***Could not create Makefile due to some reason, probably lack of necessarylibraries and/or headers.  Check the mkmf.log file for more details.  You mayneed 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/bevan/.rvm/rubies/ruby-2.3.0/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}/libTo see why this extension failed to compile, please check the mkmf.log which can be found here:  /Users/bevan/.rvm/gems/ruby-2.3.0/extensions/x86_64-darwin-15/2.3.0/pg-0.18.2/mkmf.logextconf failed, exit code 1Gem files will remain installed in /Users/bevan/.rvm/gems/ruby-2.3.0/gems/pg-0.18.2 for inspection.Results logged to /Users/bevan/.rvm/gems/ruby-2.3.0/extensions/x86_64-darwin-15/2.3.0/pg-0.18.2/gem_make.out

当出现如上的错误的时候，解决方法如下

 

ubuntu:

1.  sudo apt-get install libpq-dev 2.  gem install pg

 

mac:

1. brew install postgresql2. gem install pg -- --with-pg-config=/Applications/Postgres.app/Contents/Versions/9.4/bin/pg_config