Ruby on rails 当我尝试安装pg gem时，是什么导致了这个错误？

我正在尝试安装

我得到这个错误：

Installing pg (0.10.1) with native extensions /Users/ben/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/rubygems/installer.rb:483:in `rescue in block in build_extensions': ERROR: Failed to build gem native extension. (Gem::Installer::ExtensionBuildError)

/Users/ben/.rvm/rubies/ruby-1.9.2-p0/bin/ruby extconf.rb --with-pg-config=/users/ben/postgresql/bin
Using config values from /users/ben/postgresql/bin
*** 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/ben/.rvm/rubies/ruby-1.9.2-p0/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
extconf.rb:13:in ``': Permission denied - /users/ben/postgresql/bin --includedir (Errno::EACCES)
    from extconf.rb:13:in `<main>'

我在跑步：

Rails 3.0.1
Ruby 1.9.2
OSX 10.6.6

---

如果其他人有此问题，则错误是由以下原因引起的：

bundle config build.pg --with-pg-config=/users/ben/postgresql/bin

应该是

bundle config build.pg --with-pg-config=/users/ben/postgresql/bin/pg_config

---

如果其他人有此问题，则错误是由以下原因引起的：

bundle config build.pg --with-pg-config=/users/ben/postgresql/bin

应该是

bundle config build.pg --with-pg-config=/users/ben/postgresql/bin/pg_config