在我的情况下，上述建议对我不起作用。我的情况有点不同。

当我尝试使用gem安装bundle安装bundle ..但我正在

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /Library/Ruby/Gems/2.3.0 directory.

然后我尝试使用sudo宝石安装捆绑器，然后我得到

ERROR:  While executing gem ... (Gem::FilePermissionError)
  You don't have write permissions for the /usr/bin directory.

然后我尝试用sudo gem安装捆绑器-n /usr/local/bin(只是/usr/bin力在我的情况下工作)。

然后成功安装了捆扎机

编辑:我使用MacOS，也许/usr/bin不适合我的原因(https://stackoverflow.com/a/34989655/3786657评论)

我在运行bin/dev时得到这个错误

bin/dev
/Users/st/.rbenv/versions/3.0.3/lib/ruby/site_ruby/3.0.0/rubygems.rb:265:in `find_spec_for_exe': can't find gem foreman (>= 0.a) with executable foreman (Gem::GemNotFoundException)
    from /Users/st/.rbenv/versions/3.0.3/lib/ruby/site_ruby/3.0.0/rubygems.rb:284:in `activate_bin_path'
    from /Users/st/.rbenv/versions/3.0.3/bin/foreman:25:in `<main>'

我尝试了很多方法，但解决问题的方法很简单:

gem install foreman

现在bin/dev又可以正常工作了。

我今天也遇到了同样的问题。我通过删除旧rvm. bashrc中的任何PATH来解决这个问题。

更新:

根据@noraj的回答和@Niels Kristian的评论，下面的命令应该可以完成这项工作。

gem update --system
bundle install

我写这个是为了防止有人遇到我这样的问题。

宝石安装捆绑器显示，一切安装良好。

Fetching: bundler-1.16.0.gem (100%)
Successfully installed bundler-1.16.0
Parsing documentation for bundler-1.16.0
Installing ri documentation for bundler-1.16.0
Done installing documentation for bundler after 7 seconds
1 gem installed

当我输入bundle时，有一个错误:

/Users/nikkov/.rvm/gems/ruby-2.4.0/bin/bundle:23:in `load': cannot load such file -- /Users/nikkov/.rvm/rubies/ruby-2.4.0/lib/ruby/gems/2.4.0/gems/bundler-1.16.0/exe/bundle (LoadError)
    from /Users/nikkov/.rvm/gems/ruby-2.4.0/bin/bundle:23:in `<main>'
    from /Users/nikkov/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `eval'
    from /Users/nikkov/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `<main>'

在/Users/nikkov/.rvm/rubies/ruby-2.4.0/lib/ruby/gems/2.4.0/gems/文件夹中没有bunder -1.16.0文件夹。

我用sudo宝石安装捆绑器修复了这个问题

真正的答案在这里，如果你试图安装bundler 2.0.1或2.0.0，因为bundler需要RubyGems v3.0.0

Yesterday I released Bundler 2.0 that introduced a number of breaking changes. One of the those changes was setting Bundler to require RubyGems v3.0.0. After making the release, it has become clear that lots of our users are running into issues with Bundler 2 requiring a really new version of RubyGems. We have been listening closely to feedback from users and have decided to relax the RubyGems requirement to v2.5.0 at minimum. We have released a new Bundler version, v2.0.1, that adjusts this requirement.

更多信息，请参见:https://bundler.io/blog/2019/01/04/an-update-on-the-bundler-2-release.html

Gemfile开放。锁定，这是在你的应用程序文件夹的根目录。滚动到文件的末尾，查看使用的绑定器版本。然后确保你安装了使用的捆绑包版本:

gem install bundler -v x.xx.xx

或者-删除Gemfile。锁定和捆绑，如果你有更高的捆绑版本安装。

选择在你，我的朋友。