How to Convert All Excel Sheets to CSV With Macros. Excel's Save As command lets you save a single worksheet in the CSV (comma seperated value) format, but not an entire workbook. Saving ...

If you need to convert that file from CSV to JSON, you can do that with the csvjson command like so: csvjson clients.csv > clients.json Csvkit has a couple of other handy tricks up its sleeve.

If the DAT file you're trying to open is text, you can convert the file into text in the Microsoft Excel program by first saving it as a CSV file.