Bundler serves two primary purposes:

1. it helps you to install the correct gem versions
2. it constrains the load path to the correct gem versions at runtime

Assuming you’re using Bundler to constrain your runtime environment (which you are if you’re using Rails 3 defaults), then you are likely prefixing most shell commands with bundle exec.

We interrupt this post for an important update:

Two important pieces of information in the comments:

1. Prepending ./bin to your path exposes a serious security risk. Proceed with caution.
2. rvm >= 1.6.18 + bundler >= 1.0.5 removes the need for this altogether.

We now return you to our regularly scheduled post:

Here’s a little tip to help save you the prefix, without adding any aliases or functions to your environment.

bundle install --binstubs
export PATH=./bin:$PATH

bundle install --binstubs creates a bin directory at the root of your project, and fills it with Bundler-enabled wrappers for all of the executables installed by the gems listed in your Gemfile. This enables you to type bin/rake instead of bundle exec rake, for example, ensuring that the correct version of rake is loaded.

Now prepend ./bin to your path and you can just type rake.