#!/bin/sh

_err_fatal() {
  printf "%s\n" "$*"
  exit 1
}

certfile="${1}"

command -v curl 2> /dev/null || _err_fatal "This script requires cURL. Please install it first."
test -z "${certfile}" && _err_fatal "Please specify certificate file."
test -f "${certfile}" && _err_fatal "Error reading certificate file ${certfile}."

for ca in sub.class1.server.ca.pem ca.pem; do
  curl "http://www.startssl.com/certs/${ca}" >> "${certfile}"
done