You can install Rails in a Fedora system with these commands…

yum -y install ruby ruby-devel ruby-irb ruby-libs ruby-rdoc ruby-ri rubygems
sudo gem update
sudo gem install rails --include-dependencies

This will let you run a linux command based on the success of anther command. Note: This will only work in bash shell.

ruby Create_PDF.rb && if [ $? == 0 ]; then kpdf report.pdf; fi

This will let you find whether a variable is defined in ruby.

if(defined? var_name) then
    print var_name + " is set"
end

Use this command to install a ruby gem in Linux - you must be connected to the net

sudo gem install ruport -y