Is that process running? pgrep!
If I want to ask the operating system if a process is running I typically use something like:
$ ps -ax | grep rails
But the output reports two processes, the rails process that is running and the actual grep. Once trick to get past this is:
$ ps -ax | grep [r]ails
So that the grep looks for a process that starts with r followed by ails but can't find it because the r is followed by ].
But this is an old problem with a fairly old solution. Both mac and linux have a pgrep program.
$ pgrep ruby
44761
Which returns the pid of the process you're looking for. To get more information about the program and its arguments use the -lf flags.
$ pgrep -lf ruby
44761 /Users/devuser/.rvm/rubies/ruby-2.3.1/bin/ruby bin/rails s