Using cURL to download a Google Spreadsheet as .xls (Excel)

First obtain a Authentication Token:
# curl https://www.google.com/accounts/ClientLogin -d Email=user@quantumcrypto.de -d Passwd=mysecretpassword -d accountType=HOSTED_OR_GOOGLE  -d source=cURL-Example -d service=wise

This will return something that looks as follows:

SID=DQAAAHYBADCv2pSv7nflacDNwz3zEDUGtrSvNVDcpkSfddi77b3U5sEaHmP8YLWhmA36F9rk85mL8J5dqo4apn0T1vKz0fPGI9Xtnuet6cuE2ZzYvrNIwbSC_HjTqF4zudNQnnlDuD2wqZT-g1qXI8KhGAQZV4NexHZoQPlabTsGuRZeIBxj1A LSID=EUBBBIaBADCl-kNxvRVmcQghpt3cqSMfEooKR9flLOUZqwgP9OrZS83gse-KSdTNeXhxsET7FYenDhceP9lIPOmesH-t9qh-AWUHjjMdZEbUNeF9mWyzln6Z-FajaiG-cVFkqW0ZJ8ZbnCP30xXj6xFK6QxaAcqy_9Pej8jhEnxS9E61ftQGPg Auth=EUBBIacAAADK-kNxvRVmcQghpt3cqSMfEooLNMflLNIQqwgP9OrZS83gs-KSdTNeXhxsET7FYePWmaD8Vsy1V4LSUGMUP48Je2TO8OcjBj6HgAtPhiZeX-gKDfagZDK44j4n-Tkb44nhOnp2_QPSnBj3Z2vYwOEDjjG3Q53aQVC2132JKOuGh

To export a Google Spreadsheet as .xls (Excel):
# curl --silent --header "Authorization: GoogleLogin auth=AUTHKEY" http://spreadsheets.google.com/feeds/download/spreadsheets/Export?key=spreadsheetkey&exportFormat=xls

exportFormat Parameter Value	Format of the returned Spreadsheet
xls	XLS (Microsoft Excel)
csv	CSV (Comma Separated Value)
pdf	PDF (Portable Document Format)
ods	ODS (Open Document Spreadsheet)
tsv	TSV (Tab Separated Value)
html	HTML Format