nginx_gen_cert.rb

#!/usr/bin/env ruby
# Pass in the name of the site you wich to create a cert for

domain_name =  ARGV[0]

if domain_name == nil
  puts "Y U No give me a domain name?"
else
  system "openssl genrsa -out #{domain_name}.key 1024"
  system "openssl req -new -key #{domain_name}.key -out #{domain_name}.csr -subj '/C=US/ST=NJ/L=Monroe/O=MyCompany/OU=IT/CN=#{domain_name}'"
  system "cp #{domain_name}.key #{domain_name}.key.bak"
  system "openssl rsa -in #{domain_name}.key.bak -out #{domain_name}.key"
  system "openssl x509 -req -days 365 -in #{domain_name}.csr -signkey #{domain_name}.key -out #{domain_name}.crt"
  system "mkdir -p /usr/local/etc/nginx/ssl"
  system "mv #{domain_name}.* /usr/local/etc/nginx/ssl"
end

I think you need to create the logs Dir and touch the logs files...

#!/usr/bin/env ruby
# Pass in the name of the site you wich to create a cert for

domain_name =  ARGV[0]

if domain_name == nil
  puts "Y U No give me a domain name?"
else
  system "openssl genrsa -out #{domain_name}.key 1024"
  system "openssl req -new -key #{domain_name}.key -out #{domain_name}.csr -subj '/C=US/ST=NJ/L=Monroe/O=MyCompany/OU=IT/CN=#{domain_name}'"
  system "cp #{domain_name}.key #{domain_name}.key.bak"
  system "openssl rsa -in #{domain_name}.key.bak -out #{domain_name}.key"
  system "openssl x509 -req -days 365 -in #{domain_name}.csr -signkey #{domain_name}.key -out #{domain_name}.crt"
  system "mkdir -p /usr/local/etc/nginx/ssl"
  system "mv #{domain_name}.* /usr/local/etc/nginx/ssl"
  system "mkdir -p /usr/local/etc/nginx/logs"
  system "touch /usr/local/etc/nginx/logs/#{domain_name}-ssl-access.log"
  system "touch /usr/local/etc/nginx/logs/#{domain_name}-ssl-error.log"
end