Re: Re: Compiling Software
  By: MIKE POWELL to ROB MCCART on Wed May 24 2006 01:10 pm

 > >Yes..  And recent Google testing - it being an independant site
 > >used by people from all places and OS's - found that about 26%
 > >of users are still running Win 98 and about 48% are running Win XP
 > >I think it was. The rest were in the remaining 26% or so..
 > >No other single OS (All Linux versions considered a single OS) was
 > >over 10% if I recall.
 > 
 > I've asked this before, but never really got an answer.  How do they know
 > which OS you are running?  Just because a browser identifies itself as IE,
 > which would idicate that they are probably running windows, does not mean
 > that it actually is IE.
 > 
 > Mike

Hi Mike,

Most CGI scripts (PHP, ColdFusion, ASP, etc) will have an environment 
variable set by the user's browser called User Agent or HTTP User Agent 
that comes from their browser.  Every version of a browser should have its 
own unique agent for that OS, so this is generally how folks find out.  SO 
like when I visit a website on Win XP Pro in Firefox, here's the content of 
my browser agent variable:

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.3) Gecko/20060426 
Firefox/1.5.0.3

Here it is in IE on Win XP:

Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Maxthon; .NET CLR 
1.1.4322; InfoPath.1; .NET CLR 2.0.50727)


And if I were on Safari on OSX or Firefox on Linux, it would show something 
different as well. I even remoted into my home computer and tried it from 
Lynx, and here's what it gave me:

Lynx/2.8.5rel.1 libwww-FM/2.14 SSL-MM/1.4.1 OpenSSL/0.9.7g

So basically you have to identify the OS from this variable.  Some folks 
will look for key words, like IE and Windows to know it's, well IE on 
WIndows, others IE and Mac, or anything else.  But be warned that this 
variable can be edited by the user.  I have seen some sites that blindly 
block non-IE browsers because they don't want to bother testing or 
supporting folks on anything but IE, but changing the User Agent to say 
you're using IE makes the site work fine...

Anywhoo, hope this helps.  Google for HTTP_USER_AGENT and you'll find much 
more on this topic.

Sam


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Sam Alexander - sam.alexander(at)sidebandbbs(dot)com
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understanding, Understanding is not wisdom." -- Cliff Stoll 


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