From: "Wayne E. Seguin" <wayneeseguin@...>
Date: 2007-07-18T23:33:33+09:00
Subject: Re: Validating an Image file is an image file

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On Jul 18, 2007, at 10:25 , John Joyce wrote:
> I know how to validate a file based only on the file name dot  
> extension, but this seems wholly insecure to me.
> I feel that just testing for .jpg, .png, .jpeg, .gif, etc... is not  
> enough.
> Clearly renaming a file to anything at all is easy to do.
> How can I read into the file and check to see if it is is actually  
> a file of a given image type? Is there file header info to look for ?
> Such as a particular byte sequence at a particular location in the  
> file?
>
>
> John Joyce

Use the unix file command `file #{file_name}`

example:

 > file the.gif
the.gif: GIF image data, version 89a, 91 x 91

--
Wayne E. Seguin
Sr. Systems Architect & Systems Admin
wayneseguin@gmail.com




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