How to run a specific version of a ruby gem

I am running brakeman outside of my Gemfile, so am not using bundler.

If I do gem list, I can see I have the following for brakeman

brakeman (3.3.3, 3.3.2, 3.1.4, 3.1.2)

But if I do brakeman --version, I get

brakeman 3.1.2

so I am not using the latest version. If I do gem update brakeman or

gem update brakeman, '3.3.3,

I get

Updating installed gems
Nothing to update

So how do I run brakeman version 3.3.3?

Solution

I can't reproduce this issue, but I can think of a few reasons why this might happen:

Bundler artifacts (perhaps in .bundle/) pointing to the old version. Try running in a different directory and see if it still happens
A bug in RubyGems (try gem update --system)
During install, it asked if you wanted to replace the brakeman binary and you selected "no"
If you are using a Ruby version manager, maybe one version is on a different path than another (like a system gem versus one managed by rvm)
Any number of GEM_PATH, bundler, gem, rvm weirdness that sometimes occurs

In any case, if I were you I'd gem uninstall brakeman, remove all versions, and install fresh. If you are using rvm, start with a fresh gemset or rvm gemset empty the current one.