谦卑地寻求帮助。学习Ruby on Rails。
观看此YouTube视频https://www.youtube.com/watch?v=7EzzoULwWx8#t=480，并在9:10，教师输入：
psql
bash shell与我的不同，并且在终端提示符下没有$。
当我尝试：
Michels-MacBook-Pro:~ michelfrechette$ pqsl
这些是我的结果：
Michels-MacBook-Pro:~ michelfrechette$ psql
psql: could not connect to server: No such file or directory
Is the server running locally and accepting
connections on Unix domain socket "/tmp/.s.PGSQL.5432"?
Michels-MacBook-Pro:~ michelfrechette$
使用：PostgreSQL 9.3.5
我错过了什么？有人可以提供指导吗？谢谢。
其他信息：
Michels-MacBook-Pro:~ michelfrechette$ heroku --v
/Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/tmpdir.rb:85:in `mkdir': ERROR: Failed to build gem native extension. (Gem::Ext::BuildError)
Permission denied @ dir_s_mkdir - ./.gem.20141013-60662-6x4qt9
Gem files will remain installed in /Users/michelfrechette/.rvm/gems/ruby-2.0.0- p481@global/gems/executable-hooks-1.3.2 for inspection.
Results logged to /Users/michelfrechette/.rvm/gems/ruby-2.0.0-p481@global/extensions/x86_64-darwin-13/2.1.0-static/executable-hooks-1.3.2/gem_make.out
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/tmpdir.rb:85:in `block in mktmpdir'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/tmpdir.rb:142:in `create'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/tmpdir.rb:85:in `mktmpdir'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/ext_conf_builder.rb:14:in `build'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:161:in `block (2 levels) in build_extension'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:160:in `chdir'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:160:in `block in build_extension'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:159:in `synchronize'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:159:in `build_extension'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:198:in `block in build_extensions'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:195:in `each'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/ext/builder.rb:195:in `build_extensions'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/specification.rb:1436:in `block in build_extensions'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/user_interaction.rb:45:in `use_ui'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/specification.rb:1434:in `build_extensions'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/stub_specification.rb:60:in `build_extensions'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/basic_specification.rb:56:in `contains_requirable_file?'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/specification.rb:925:in `block in find_inactive_by_path'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/specification.rb:924:in `each'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/specification.rb:924:in `find'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/specification.rb:924:in `find_inactive_by_path'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems.rb:185:in `try_activate'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:132:in `rescue in require'
from /Users/michelfrechette/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:144:in `require'
from /Users/michelfrechette/.rvm/gems/ruby-2.0.0-p481@railstutorial_rails_4_0/bin/ruby_executable_hooks:9:in `<main>'
其他信息：
Michels-MacBook-Pro:~ michelfrechette$ ps -ef | grep postgres
501 60896 60710 0 6:06am ttys000 0:00.00 grep postgres
Michels-MacBook-Pro:~ michelfrechette$ gem install pg
Error loading RubyGems plugin "/Users/michelfrechette/.rvm/gems/ruby-2.0.0- p481@global/gems/executable-hooks-1.3.2/lib/rubygems_plugin.rb": ERROR: Failed to build gem native extension.
Permission denied @ dir_s_mkdir - ./.gem.20141013-60906-9b5gwl
Gem files will remain installed in /Users/michelfrechette/.rvm/gems/ruby-2.0.0- p481@global/gems/executable-hooks-1.3.2 for inspection.
Results logged to /Users/michelfrechette/.rvm/gems/ruby-2.0.0- p481@global/extensions/x86_64-darwin-13/2.1.0-static/executable-hooks-1.3.2/gem_make.out
(Gem::Ext::BuildError)
Error loading RubyGems plugin "/Users/michelfrechette/.rvm/gems/ruby-2.0.0- p481@global/gems/gem-wrappers-1.2.5/lib/rubygems_plugin.rb": ERROR: Failed to build gem native extension.
Permission denied @ dir_s_mkdir - ./.gem.20141013-60906-m2ih6w
Gem files will remain installed in /Users/michelfrechette/.rvm/gems/ruby-2.0.0- p481@global/gems/executable-hooks-1.3.2 for inspection.
Results logged to /Users/michelfrechette/.rvm/gems/ruby-2.0.0- p481@global/extensions/x86_64-darwin-13/2.1.0-static/executable-hooks-1.3.2/gem_make.out
(Gem::Ext::BuildError)
Building native extensions. This could take a while...
Successfully installed pg-0.17.1
invalid options: -f fivefish
(invalid options are ignored)
Parsing documentation for pg-0.17.1
Done installing documentation for pg after 1 seconds
1 gem installed
Michels-MacBook-Pro:~ michelfrechette$