Using cURL via CLI to debug Magento's XML-RPC API calls

gistfile1.html

If any exceptions are encountered due to 3rd party/local observers debugging can be questionable as no log 
is created to determine root cause.  This mini doc covers how to use the XML-RPC API in Magento to test a 
product update API call that is returning a 500 internal server error due to an observer firing in 3rd party 
code.  Using some simple XML docs prepared for login and the request it is easier to see the Fatal error 
returned for a request, in this example product.update.

xmlrpclogin.xml contents:
 
<?xml version="1.0"?>
<methodCall>
   <methodName>login</methodName>
   <params>
     <param>
       <value>username</value>
     </param>
     <param>
       <value>password</value>
     </param>
   </params>
</methodCall>

 CURL call with login via CLI:
 
 curl --data @xmlrpclogin.xml http://domain.com/api/xmlrpc/
 
 Session ID returned, copy and insert
 
 xmlrpcproductupdate.xml contents:
 
 <?xml version="1.0" encoding="UTF-8"?>
<methodCall>
   <methodName>call</methodName>
   <params>
      <param>
         <value>
            <string><![CDATA[INSERT SESSION ID HERE]]></string>
         </value>
      </param>
      <param>
         <value>
            <string><![CDATA[catalog_product.update]]></string>
         </value>
      </param>
      <param>
         <value>
            <array>
               <data>
                  <value>
                     <string><![CDATA[product_sku]]></string>
                  </value>
                  <value>
                     <struct>
                        <member>
                           <name>visibility</name>
                           <value>
                              <i4>1</i4>
                           </value>
                        </member>
                        <member>
                           <name>status</name>
                           <value>
                              <string />
                           </value>
                        </member>
                        <member>
                           <name>name</name>
                           <value>
                              <string><![CDATA[Product Name]]></string>
                           </value>
                        </member>
                        <member>
                           <name>categories</name>
                           <value>
                              <array>
                                 <data />
                              </array>
                           </value>
                        </member>
                        <member>
                           <name>description</name>
                           <value>
                              <string><![CDATA[Product Description Here.]]></string>
                           </value>
                        </member>
                        <member>
                           <name>websites</name>
                           <value>
                              <array>
                                 <data />
                              </array>
                           </value>
                        </member>
                        <member>
                           <name>additional_attributes</name>
                           <value>
                              <struct>
                                 <member>
                                    <name>single_data</name>
                                    <value>
                                       <struct />
                                    </value>
                                 </member>
                              </struct>
                           </value>
                        </member>
                        <member>
                           <name>price</name>
                           <value>
                              <double>29.90</double>
                           </value>
                        </member>
                        <member>
                           <name>msrp_enabled</name>
                           <value>
                              <string />
                           </value>
                        </member>
                     </struct>
                  </value>
               </data>
            </array>
         </value>
      </param>
   </params>
</methodCall>
 
 curl --data @xmlrpcproductupdate.xml http://domain.com/api/xmlrpc/