grab value between two strings with sed?

I have the following data on one line:

<a href="#page-metadata-start" class="assistive">Go to start of metadata</a>
<div id="page-metadata-end" class="assistive"></div>

        <fieldset class="hidden parameters">
                        <input type="hidden" title="browsePageTreeMode" value="view">
        </fieldset>

        <div class="wiki-content">
           <p>(openissues)81(/openissues)</p><p>(assignstoday)0(/assignstoday)</p><p>(assignsweek)2(/assignsweek)</p><p>(replyissues)6(/replyissues)<开发者_Go百科;/p><p>(wrapissues)26(/wrapissues)</p>
        </div>

I'd like to grab the value for "openissues" for example, but I can't figure out to properly retrieve this. One of the things I tried is the following command:

sed -n '/(assignstoday)/,/(\/assignstoday)/p' ~/test.txt

Any help?

sed 's/.*(openissues)\(.*\)(\/openissues).*/\1/' test.txt

a quick hack to possibly meet your edited requirement:

sed -n '/openissues/p' test.txt | sed  's/.*(openissues)\(.*\)(\/openissues).*/\1/'

but regexes are really not the way to go when parsing HTML.

I'd try

VALUE=openissues
sed  's@.*('"$VALUE"')\([^(]\+\).*@\1@'

that is, replace everything except the contents of what you are searching, with that content.

edit: Now I see Neil's answer, that's practically the same, accept his. I leave my answer for the customization of which value you want to extract.