How do I see if the passenger gem is installed

Question

Not sure why this might be happening? I'm trying to get a ruby app I use working through Apache on port 80, but am stumbling at every hurdle :)

root../public/htdocs# bundle show passenger
Could not find gem 'passenger'.
Did you mean passenger?
root../public/htdocs# gem install passenger
Building native extensions.  This could take a while...
Successfully installed passenger-5.0.21
1 gem installed
Installing ri documentation for passenger-5.0.21...
Installing RDoc documentation for passenger-5.0.21...
root../public/htdocs# bundle show passenger
Could not find gem 'passenger'.
Did you mean passenger?

Answer 1

You provided no bakcground info about the OS you are running , the package manager you using to manage different versions of Ruby , gems eg "rbenv , rvm ....etc" how you are managing your gems .. eg locally , globally , via gemset... etc . So , generally speaking you can either , run gem list and grep for the name of the gem like below with the gem qualifier as an example :

user@user-SVE1411EGXB:~/shop_app/depot2$ gem list | grep uglif*
uglifier (2.7.2, 2.6.0, 2.5.3, 2.5.1, 2.5.0, 2.4.0, 1.2.7, 1.2.4)

Or you can specify by passing the name of the gem as an ARG to gem list

user@user-SVE1411EGXB:~/shop_app/depot2$ gem list uglifier

*** LOCAL GEMS ***

uglifier (2.7.2, 2.6.0, 2.5.3, 2.5.1, 2.5.0, 2.4.0, 1.2.7, 1.2.4)
user@user-SVE1411EGXB:~/shop_app/depot2$