So, I'm in the process of writing some code for SAS and I realized I have to save the file as filename.sas. My professor mentioned that I would have to use note pad or another text editor on my computer.
How can I use TextEdit on the Mac to save a .sas file? Opening TextEdit, adding some text, and saving causes the file to have a .rtf or .odt extension added to it.
Should probably add that my mac version is 10.5.8
Your Mac comes with TextEdit, which is a perfectly good basic text editor. Be sure to choose Format > Make Plain Text so that you get a text file. Be sure to uncheck Hide Extension when you save, and provide the .sas extension manually. Or you can change the extension later using File > Get Info in the Finder.
You also have pico, vim, vi, emacs, and probably a host of others in the Terminal.
Above mentioned solutions are best suitable for older mac os versions.
But for the latest mac os version(Mojave or later) try with nano or other command-line text editors.
来源：https://stackoverflow.com/questions/23976219/how-do-i-save-a-textedit-mac-file-with-a-custom-extension-sas