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A similar question was asked here but the answer refers to something called QL Stephen, which only claims to preview files with no extension. I need something that will show previews of files with extensions that are unknown to the Finder. They are all plain-text files. And, it needs to run on Lion (10.7).

To clarify: I'm not looking for a default QL for any unknown extension, but rather for one that will preview certain specific extensions (e.g., .sps, .fort) as plain text.

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Since all unknown file extensions are not necessarily text, this is a bad idea. – Slomojo Aug 30 '11 at 2:00
A QuickLook plug-in version of HexFiend seems like the ideal unknown/default previewer, if QuickLook could be thus configured. – Daniel Aug 30 '11 at 2:41
@slomojo: good point; I didn't mean all unknown file extensions, but rather several specific ones that are not known to the Finder. I worded that badly. – Chap Aug 30 '11 at 3:32
@Chap Harrison, I think a QL viewer that can be configured to view a set of file extensions as text (or as Daniel says, a hex dump) would be nice, for sure. I might have a look at doing this. – Slomojo Aug 30 '11 at 3:40
@Daniel: I think I gave you the wrong impression, too -- please see revised statememt of question. – Chap Aug 30 '11 at 3:40

After a quick google, maybe this is what you need?

It explains how to declare specific file types as plain text, QuickLook will use these declarations.

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Well, we're getting warmer... main problem I see is that these files I'm interested in were created by a Perl program, not an .app, so there's no Info.plist. (Also the hint claims to be 10.5 only, FWIW.) – Chap Aug 30 '11 at 3:51
@Chap Harrison, that won't matter, pick an app that you would like to open the files in, for example, TextMate or Text, and then add these extensions to that info.plist as per the article. Also the 10.5 info.plists haven't changed in this regard, so you're ok with Lion. – Slomojo Aug 30 '11 at 3:58
It may be possible to get the extension added to Text by doing Get Info, Opens with. I'll try it later and report back. – Slomojo Aug 30 '11 at 4:09
Hm - I tried the macworld technique to TextEdit, and then tried launching TextEdit (to make sure I hadn't broken anything) and it crashed with "code signature invalid"! IIRC, that's something new with Lion. Is editing Info.plist enough to have done that? – Chap Aug 30 '11 at 4:28
@Chap Harrison, Yes, editing a .plist changes the code signature for an application. – Daniel Aug 30 '11 at 4:47

You can use QuicklookStephen ( Install via Brew:

brew install Caskroom/cask/qlstephen

and then reset the Quicklook plugins:

qlmanage -r

and you should be good to go!

Tested with both files without extension and files with "unknown" extension (e.g. .nfo)

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