How to check whether a file is valid UTF-8?

Question

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.

There's a web service at W3C which appears to be dead, and I've found a Windows-only validation tool that reports invalid UTF-8 files but doesn't report which lines/characters to fix.

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.

Answer 1

You can use GNU iconv:

$ iconv -f UTF-8 your_file -o /dev/null; echo $?

Or with older versions of iconv, such as on macOS:

$ iconv -f UTF-8 your_file > /dev/null; echo $?

The command will return 0 if the file could be converted successfully, and 1 if not. Additionally, it will print out the byte offset where the invalid byte sequence occurred.

Edit: The output encoding doesn't have to be specified, it will be assumed to be UTF-8.