XEmacs *does* understand those, via the function url-retrieve. However, changing the meaning of command-line arguments program means is a recipe for trouble. Cf. the "Slow startup" thread, where Apple has gone and broken the DISPLAY variable. Trying to guess what is intended by these programs is a difficult problem. > So, I was crafting an email with thunderbird to which I attached a text > file. > But, then I wanted to view/edit that file. So, I double-clicked on it and > it asked me which application that I wanted to open it with. I chose > /usr/local/bin/xemacs which is 21.4.22. If I had picked OpenOffice, > then everything works. But, for text files, there is nothing like > XEmacs:o) There is probably a way to tell Thunderbird that it's talking to a traditional Unix program that expects to receive a file, not an URL. Traditionally in mimecap files that format would be text/plain /usr/local/bin/xemacs %s but I wouldn't be surprised if Thunderbird has usurped that format to mean URL, not file. I can't think of any quick hacks to make XEmacs do the right thing with an URL from the command line. I'll try later in the week.