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.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/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}/lib To 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.log extconf failed, exit code 1 Gem 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 postgresql
2. gem install pg -- --with-pg-config=/Applications/Postgres.app/Contents/Versions/9.4/bin/pg_config