elasticsearch/logstash — pull request #1245 by PriceChild (2014-04-10 09:17:04+00:00)
Title: Better bash test for file download fault.

-f tests for the existence of a file... curl and wget will both create a 0 length file when attempting to download, satisfying this test.

One option is to change it to a -s which ensures that the file is of non-zero length.

Or we can just check the return code of curl and wget which I believe should both use 0 for success and >0 for anything else.