Save a textedit file as CSV format

If you do not want it to save as .rtf you do not get that choice when you save the file

In TextEdit you make the choice with the Format menu > Make Plain Text (or Format menu > Make Rich Text, depending which is the format of the document when you look at the menu). If you are working in plain text it will save as .txt and if you are working in rich text it will save a .rtf.

the extension is nothing more then a help for what Application which can open the file

Really? I would have thought .rtf files have extra code for the added formatting. Simply calling a .rtf a .txt won't get rid of the formatting and if anything will make things worse because now an application will try to interpret the codes as words. I know in many other cases changing the extension can really confuse applications. Calling a .AAC file a .mp3 can really mess with a player, perhaps getting it to say the file cannot be opened and is corrupt.

An extension aids in letting the system know which applications can open a file but also lets them know the structure. Some files on my computer can be opened by 15 applications and the extension says, "Hey, I am a .rtf file. Can you open me? Yes? Then if you open me, open me interpreting me as a .rtf file. If you interpret me as a .txt file you're going to get a big surprise."

My experience is with TextEdit on Mavericks. If you do not want it to save as .rtf you do not get that choice when you save the file (I think SimpleEdit in OS9 did let you). You have to change preferences, then open the file you want to edit and save it while TE is in .txt file editing mode. Yes, it is cumbersome but is how TE works.

Get Text Wrangler, Select All in Text Edit, Copy, Paste it into Text Wrangler & save as Plain text, then in Finder change the extension to .csv from.txt...

http://www.barebones.com/products/textwrangler/

This will only work if the commas are there in the first place. The OP did not provide an example of the text line. If the line is delimited with tabs then a search and replace will have to be done to replace the tabs with commas, then save the file as a text file and change the extension to .csv

In my version of TextEdit you have to decide what format file you're going to have in the New File part of TE preferences before you open the file.

You can change the extension In finder the extension is nothing more then a help for what Application which can open the file

Best answer by far. TW was my workhorse for things like this until I finally decided its big brother (BBEdit) was worth the purchase.

was talking about csv files https://en.wikipedia.org/wiki/Comma-separated_values