Where is ${filename} coming from?

At开发者_开发百科 http://www.uploadify.com/forums/discussion/1416/uploading-to-amazon-s3/p1

Terebentina's comment. In the 'key:' section. where does ${filename} come from?

Alternatively, instead of making it look like:

"key": encodeURIComponent(encodeURIComponent("40/20091216-120535/${filename}"))

I'd like to make it look something like:

"key": encodeURIComponent(encodeURIComponent("40/20091216-120535/foobar${file_extension}"))

Sadly, ${file_extension} does not exist. Anyone know how this can be done?

EDIT:

Upon further digging. I found this http://aws.amazon.com/articles/1434 which now brings me to the conclusion that ${filename} is a variable used by S3 and not uploadify.

The questions still stands. What if we was to have specific names for all uploaded files and keep the extensions dynamic. For example: foobar.mp4, foobar.txt, foobar.flv, etc. How should we go about this?

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As described in http://aws.amazon.com/articles/1434 ${filename} is a special variable Amazon S3 uses when a file is uploaded to them.