re = /^.*?class=\"\"pinyin\"\">(.*?)<script>/m
str = '<br>
<span class=""b"">拼音:</span><span class=""pinyin"">xī<script>Setduyin(\'Duyin/xi1\')</script></span> <span class=""b"">注音:</span><span class=""pinyin"">ㄒㄧ<script>Setduyin(\'Duyin/xi1\')</script></span><br>
<span class=""b"">简体部首:</span>丨 <span class=""b"">部首笔画:</span>1 <span class=""b"">总笔画:</span>8<br><span class=""b"">ç¹ä½“部首:</span>åœã€€<span class=""b"">部首笔画:</span>2 <span class=""b"">总笔画:</span>8<br><span class=""b"">康熙å—典笔画</span>( å¥:8ï¼› )'
subst = '-'
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html