In this case the error means "trouble parsing input file". There are actually 3 problems here. I'm not sure if the 99 problem would have cropped up with any single one or whether it requires a constellation.
Mix and match white space delimiters. Rows were using tabs while the header which was added manually used spaces (in Notepad++ hit the "show all characters" toolbar button, ¶).
Fixed width delimited. The program which generated this text file left out implied digits, so
1273629 instead of
1273629.0000, however it then added an extra tab to keep the columns line up. Nothing wrong with this, it's standard practice in fixed-width delimited files, however XYToLines doesn't know about those.
Completely wrong coordinate system!
905653.9545 728436.4238 905130.0745 727809.7597 are clearly not geographic or decimal degrees numbers which can't be higher or lower than
-180.0. I should have seen this immediately but was distracted by the other errors. (This problem doesn't generate an error message, just the wrong result of zero-length lines).
UPDATE: In follow up testing, it turns out that
- Header line is optional. If left out XYToLine shows "Field1, Field2, ..."
- Only one thing to fix in order to avoid error, it is sufficient to search and replace double-tab with single (
What a sad state of affairs, "Error: 999999" happens so often it has it's own tag! Anyway, this took me a couple of hours and two days to solve, so I figure it's worth adding to the noisy heap.