For sqlite-utils issue 250 I needed to locate some test CSV files that start with a UTF-8 BOM.
\nHere's how I did that using ripgrep:
\n$ rg --multiline --encoding none '^(?-u:\\xEF\\xBB\\xBF)' --glob '*.csv' .\nThe --multiline option means the search spans multiple lines - I only want to match entire files that begin with my search term, so this means that ^ will match the start of the file, not the start of individual lines.
--encoding none runs the search against the raw bytes of the file, disabling ripgrep's default BOM detection.
--glob '*.csv' causes ripgrep to search only CSV files.
The regular expression itself looks like this:
\n^(?-u:\\xEF\\xBB\\xBF)\nThis is rust regex syntax.
\n(?-u: means \"turn OFF the u flag for the duration of this block\" - the u flag, which is on by default, causes the Rust regex engine to interpret input as unicode. So within the rest of that (...) block we can use escaped byte sequences.
Finally, \\xEF\\xBB\\xBF is the byte sequence for the UTF-8 BOM itself.