I don't know what relevance the full path of the file on the user's computer has to your web application (I'm assuming that's what you are trying to do) but you can get the filename component like this, where "file" is the id of your input field:

document.getElementById('file').value

I would suspect you cannot get the full path for security reasons.

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Chris Hope's LAMP Blog: http://www.electrictoolbox.com/