Experimental Physics and
Industrial Control System

Bill Lavender <[email protected]> · Wed, 11 Feb 2015 11:45:53 -0600

On Wed, Feb 11, 2015 at 02:28:39PM +0100, Dirk Zimoch wrote:
> On 09.02.2015 21:58, Kasemir, Kay wrote:
>> and then you need to be prepared to parse a response that looks like
>>
>> HTTP/1.1 200 OK
>> Content-Type: text/html
>> Server: Whatever
>> Cache-Control: no-cache
>> Pragma: no-cache
>> Content-Length: 97
>>
>> .. the actual data..
>
> Try regular expressions to fund the actual data in all the http noise.  
> See my example in the StreamDevice documentation:
> http://epics.web.psi.ch/software/streamdevice/doc/tipsandtricks.html#web
>
> get_title {
>   extrainput = ignore;
>   replyTimeout = 1000;
>   out "GET http://\$1\n\n";;
>   in "%+.1/(?im)<title>(.*)<\/title>/";
> }

Something like this can work with a device that always responds in a fixed
pattern.  However, you should be aware that, in general, regular expressions
cannot be used to parse arbitrary HTML.  A Stack Overflow article that
talks about this can be found here:

    http://stackoverflow.com/questions/6751105/why-its-not-possible-to-use-regex-to-parse-html-xml-a-formal-explanation-in-la

A more entertaining, though less illuminating, explanation can be found here:

    http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags/1732454#1732454

Hope this helps.

Bill Lavender

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System