create json from a certificate fullchain.pem

jsonFromFullchain.rb

#!/usr/bin/env ruby

require 'openssl'
require "json"

fullchain = ARGV[0]

cmd = %(openssl crl2pkcs7 -nocrl -certfile #{fullchain} | openssl pkcs7 -print_certs)
# if problems with empty lines occur, use this:
# cmd = %(openssl crl2pkcs7 -nocrl -certfile #{fullchain} | openssl pkcs7 -print_certs | perl -pe 's/^\n$//mg; s/-----END CERTIFICATE-----/-----END CERTIFICATE-----\n/' )
out = `#{cmd}`
certs = out.split(/\n\n/)

certsArr = []
certs.each do |certpem|
    h = {}
    cert = OpenSSL::X509::Certificate.new(certpem)
    cert.extensions.each do |ext|
        a = ext.to_a
        case a[0]
        when "subjectKeyIdentifier"
            h[a[0]] = [a[1]][0]
        when "subjectAltName"
            h[a[0]] = ([a[1]][0].split(/,/).map do |name|; name.sub!(/^\s*DNS:/,""); end).join(",")
        when "authorityKeyIdentifier"
            h[a[0]] = [a[1]][0].chop.sub(/^keyid:/,"")
        end
    end
    h["not_after"] = cert.not_after
    h["not_after_epoche"] = cert.not_after.to_i
    h["not_before"] = cert.not_before
    h["not_before_epoche"] = cert.not_before.to_i
    subHash = {}
    cert.subject.to_a.each do |e|; subHash[e[0]] = e[1]; end
    h["CN"] = subHash["CN"]
    subArray = []
    cert.subject.to_a.each do |e|; subArray << "#{e[0]}=#{e[1]}"; end
    h["subject"] = subArray.join(",")
    certsArr << h
end

puts JSON.pretty_generate(certsArr)

Output: