How to check gems ready to update?

Bundler has an outdated command. I assume you're using Bundler, of course.

If you are not using bundler, just run gem outdated and it will give you a list of outdated gems.

Example of output:

$ gem outdated                                                                                                                                                                                   
acts_as_tree (2.7.1 < 2.9.1)                                                                                                                                                                     
addressable (2.4.0 < 2.7.0)                                                                                                                                                                      
bcrypt (3.1.12 < 3.1.13)                                                                                                                                                                         
bootsnap (1.4.5 < 1.4.6)                                                                                                                                                                         
bootstrap (4.3.1 < 4.4.1)                                                                                                                                                                        
brakeman (4.7.2 < 4.8.0)                                                                                                                                                                         
cancancan (1.17.0 < 3.0.2)                                                                                                                                                                       
chart_js (1.1.0 < 1.1.1)                                                                                                                                                                         
coffee-rails (4.2.2 < 5.0.0)
combustion (0.6.0 < 1.1.2)
database_cleaner (1.8.2 < 1.8.3)
...

gem outdated will give you a list of outdated gems including version number you currently have and the latest version number.

Then to update:

• gem update GEMNAME to update a specific gem or just
• gem update to update all gems to the latest stable version