javascript regex for extracting filename from Content-Disposition header

Question

Content-disposition header contains filename which can be easily extracted, but sometimes it contains double quotes, sometimes no quotes and there are probably some other variants too. Can someone write a regex which works in all the cases.

Content-Disposition: attachment; filename=content.txt

Here are some of the possible target strings:

attachment; filename=content.txt
attachment; filename*=UTF-8''filename.txt
attachment; filename="EURO rates"; filename*=utf-8''%e2%82%ac%20rates
attachment; filename="omáèka.jpg"
and some other combinations might also be there

Answer 1

You could try something in this spirit:

filename[^;=\n]*=((['"]).*?\2|[^;\n]*)

filename      # match filename, followed by
[^;=\n]*      # anything but a ;, a = or a newline
=
(             # first capturing group
    (['"])    # either single or double quote, put it in capturing group 2
    .*?       # anything up until the first...
    \2        # matching quote (single if we found single, double if we find double)
|             # OR
    [^;\n]*   # anything but a ; or a newline
)

Your filename is in the first capturing group: http://regex101.com/r/hJ7tS6

Answer 2

Slightly modified to match my use case (strips all quotes and UTF tags)

filename\*?=['"]?(?:UTF-\d['"]*)?([^;\r\n"']*)['"]?;?

https://regex101.com/r/UhCzyI/3

Answer 3

/filename[^;=\n]*=(?:(\\?['"])(.*?)\1|(?:[^\s]+'.*?')?([^;\n]*))/i

https://regex101.com/r/hJ7tS6/51

Edit: You can also use this parser: https://github.com/Rob--W/open-in-browser/blob/master/extension/content-disposition.js