title: How to check whether a file is valid UTF-8?
body: <p>I'm processing some data files that are supposed to be valid UTF-8 but aren't, which causes the parser (not under my control) to fail. I'd like to add a stage of pre-validating the data for UTF-8 well-formedness, but I've not yet found a utility to help do this.</p>
  
  <p>There's a <a href="http://www.w3.org/2005/01/yacker/uploads/utf8-validator" rel="noreferrer">web service</a> at W3C which appears to be dead, and I've found a Windows-only validation <a href="http://web.archive.org/web/20081101142036/http://bolek.techno.cz:80/UTF8-Validator/" rel="noreferrer">tool</a> that reports invalid UTF-8 files but doesn't report which lines/characters to fix.</p>
  
  <p>I'd be happy with either a tool I can drop in and use (ideally cross-platform), or a ruby/perl script I can make part of my data loading process. </p>