它是做什么的"捆绑exec rake db:migrate"？

Question

从我的研究中,bundle exec负责在bundle的上下文中执行命令.

无论如何,我还不太了解它与命令rake db:migrate比较的不同之处bundle exec rake db:migrate.

例如在我的情况下,我执行了第一个命令,我得到的是以下错误:

$ rake db:migrate
(in c:/rails/rails_projects/soccerweb)
rake aborted!
uninitialized constant Rake::DSL
c:/Ruby192/lib/ruby/1.9.1/rake.rb:2482:in `const_missing'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/rake-0.9.2.2/lib/rake/tasklib.rb:8:in `<clas
s:TaskLib>'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/rake-0.9.2.2/lib/rake/tasklib.rb:6:in `<modu
le:Rake>'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/rake-0.9.2.2/lib/rake/tasklib.rb:3:in `<top
(required)>'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/rake-0.9.2.2/lib/rake/testtask.rb:4:in `requ
ire'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/rake-0.9.2.2/lib/rake/testtask.rb:4:in `<top
 (required)>'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/test_unit/testing.r
ake:2:in `require'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/test_unit/testing.r
ake:2:in `<top (required)>'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/test_unit/railtie.r
b:12:in `load'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/test_unit/railtie.r
b:12:in `block in <class:TestUnitRailtie>'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/railtie.rb:183:in `
call'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/railtie.rb:183:in `
block in load_tasks'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/railtie.rb:183:in `
each'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/railtie.rb:183:in `
load_tasks'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/engine.rb:396:in `b
lock in load_tasks'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/application/railtie
s.rb:8:in `each'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/application/railtie
s.rb:8:in `all'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/engine.rb:396:in `l
oad_tasks'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/application.rb:103:
in `load_tasks'
c:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.1.1/lib/rails/railtie/configurabl
e.rb:30:in `method_missing'
c:/rails/rails_projects/soccerweb/Rakefile:7:in `<top (required)>'
c:/Ruby192/lib/ruby/1.9.1/rake.rb:2373:in `load'
c:/Ruby192/lib/ruby/1.9.1/rake.rb:2373:in `raw_load_rakefile'
c:/Ruby192/lib/ruby/1.9.1/rake.rb:2007:in `block in load_rakefile'
c:/Ruby192/lib/ruby/1.9.1/rake.rb:2058:in `standard_exception_handling'
c:/Ruby192/lib/ruby/1.9.1/rake.rb:2006:in `load_rakefile'
c:/Ruby192/lib/ruby/1.9.1/rake.rb:1991:in `run'
c:/Ruby192/bin/rake:31:in `<main>'

但是当我在"rake db:migrate"命令之前使用"bundle exec"时,一切都正常地为我工作!

谁能对我有所了解？

Answer 1

bundle exec rake运行rake您在其中指定的版本Gemfile.rake您可以在其中找到的默认版本$PATH可能与执行的默认版本不同bundle exec rake.

您遇到的问题已在单独的问题中介绍.你bundle exec rake最有可能运行0.8.7并且rake你的$PATH是一个受此问题影响的新版本.

引自man bundle exec:

bundle exec对shell环境进行了一些更改,然后执行完全指定的命令.

• (......)
• 将包含可执行文件的目录(如rails,rspec,rackup)放在$ PATH上