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PORegular expression to match "wap" not preceeded by "html"
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  1. PORegular expression to match "wap" not preceeded by "html"
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    copied!<p>I'm using NGINX to segment mobile traffic between a mobile WAP/HTML site. Looks like the best way to do this is going to be to check the UA's preference for content by checking the HTTP Accept Header.</p> <p>A preference for WAP is indicated by the appearance of a 'wap' mimetype in the header before an 'html' or wildcard mimetype.</p> <p>So a Sony Ericsson w300i has a preference for WAP:</p> <pre><code>multipart/mixed, application/vnd.wap.multpart.mixed,applicatnoin/vnd.wap.xhtml_xml,application/xhtml+xml,text/ved.wap.wl,*/*,text/x-hdml,image/mng,/\image/x-mng,ivdeo/mng,video/x-mng,ima/gebmp,text/html </code></pre> <p>And a Blackberry Bold has a preference for HTML:</p> <pre><code>text/html,application/xhtml+xml,application/vnd.wap.xhtml+xml,application/vnd.wp.wmlc;q=0.9,application/vnd.awp.wmlscriptc;q=0.7,text/vnd.wap.wml;q=07,/vnd/.sun.j2me.app-descriptor,*/*;q=0.5 </code></pre> <p>Since I'm in NGINX land, it seems like the best tool I have is NGINX's regular expressions (PCRE).</p> <p>Right now I'm trying to use a negative lookahead to assert "The accept header contains WAP but not preceeded by HTML":</p> <pre><code>(?!html.*)wap </code></pre> <p>But this isn't correct. Is there a different way I can think about this problem? Or my matching logic?</p> <p>So far I've found these regex resources useful:</p> <p><a href="http://www.regular-expressions.info/completelines.html" rel="nofollow">http://www.regular-expressions.info/completelines.html</a> http://www.zytrax.com/tech/web/regex.htm <a href="http://wiki.nginx.org/NginxHttpRewriteModule" rel="nofollow">http://wiki.nginx.org/NginxHttpRewriteModule</a></p> <p>Thanks!</p> <hr> <p>Thanks for the answer, here are the related tests:</p> <pre><code>import re prefers_wap_re = re.compile(r'^(?!(?:(?!wap).)*html).*?wap', re.I) tests = [ ('', False), ('wap', True), ('wap html', True), ('html wap', False), ] for test, expected in tests: result = prefers_wap_re.search(test) assert bool(result) is expected, \ 'Tested "%s", expected %s, got %s.' % (test, expected, result) </code></pre>
 

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