Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Thu, 12 Feb 2015 12:07:34 +0100

On 11.02.2015 18:45, Bill Lavender wrote:

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

Bill is right. I also mention this in my documentation:

"But this only works if the order of the values is predictible.

StreamDevice is not an XML parser! It always reads sequentially."

The web page must have a fixed format. In particular all values to parse

must always be in the same order.

Dirk

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System