After having the unpleasant surprise that Comma Seperated Value (CSV) files are not necessarily comma-separated, I'm trying to find out if there is any way to detect what the regional settings list separator value is on the client machine from http request.

Scenario is as follows: A user can download some data in CSV format from web site (RoR, if it matters). That CSV file is generated on the fly, sent to the user, and most of the time double-clicked and opened in MS Excel on Windows machine at the destination. Now, if the user has ',' set as the list separator, the data is properly arranged in columns, but if any other separator (';' is widely used here) is set, it all just gets thrown into a single column. So, is there any way to detect what separator is used on the client machine, and generate the file accordingly?

I have a sinking feeling that it is not, but I'd like to be sure before I pass the 'can't be done, sorry' line to the customer :)