I posted this the last time there was a discussion about CSV and excel:

If you are generating the CSV yourself, save yourself some agony and just wrap the text in =""

    $ cat test.csv
    ="12.34567890124312341234123412341234",="1-5"
    $ open -a Microsoft\ Excel test.csv

https://news.ycombinator.com/item?id=5514587

Explanation:

It uses another auto trick: if the leading character is '=', the result is treated as a formula.

Thus, you can actually write formulas in your CSV and excel will interpret appropriately:

    $ cat test.csv
    =1+1,="1-5"
    $ open -a Microsoft\ Excel test.csv

You should see the value '2' (with content `=1+1`)

https://news.ycombinator.com/item?id=5514704

An alternative solution that works is some situations is to format the column as "Text". However you must do this before pasting the data into the cells or else it will already be converted. I use this technique for zip codes which can have leading zeros.

"The problem is that the CSV file format has no reliable mechanism to mark a column as text( )."*

The problem is that there is NO such thing a "the CSV file format". There's only a lot of different interpretations of how to store data in forms of rows with fields separated by commas or semicolons or whatnot, with every software package having slightly different ideas.

Save the world, use S-expressions or JSON if you write something new.

CSV is not the issue here; Excel's automagic conversions are. If it could open JSON, it'd extract the values, then apply it's magic. So your JSON string "DEC1" would still be converted (JSON doesn't have a date type).

The point of my comment was mainly that "by rewriting data cells in spreadsheets" is a poor way to describe the bad import behavior of Excel. A CSV is an ill specified structured text file, not a spreadsheet (most spreadsheets have some sort of type information for each cell, who knows whether it is intentional and accurate and so forth, but it is there).

In that context, "in an Excel file" meant "in a native Excel file".

> most spreadsheets have some sort of type information for each cell ...

Yes, but the problem is that, without some knowledge and care on the part of the operator, the data type will be established during the import, not in advance, and on a cell-by-cell basis.