# Writing Your Own Draft Message Editor(s)

You may want to do more than an editor like vi or emacs can do to a draft message. For instance, you might want to start prompter on the new draft, then run a second editor to fill in the body. Or you might want to do something automatically each time a draft message is edited, like updating a mail message log. Or you could customize the way that a particular MH program, such as dist, handles a draft message. These are all good reasons to write a special editing shell script.

There are five things to know before you write your editor script:

1. Each of the four mail composition commands will make a draft message for you. If no other editor (including prompter) has touched it, the draft will contain:
   - For comp, an empty copy of the components file. (Exception: with comp -use, draft will be exactly as it was left before.)
   - For repl, the result of the replcomps file, with the original message filtered through the -filter file (if you used one).
   - For forw, a copy of the forwcomps file, with the forwarded message(s) (filtered through -format or -filter if you used one).
   - For dist, a copy of the distcomps file.
   For more information, see the Section Making the Draft from the Template File.
2. The full pathname of the draft message will be in the `$1` parameter.
3. You can use the environment variables listed in the Table Environment Variables that MH Sets.
4. Your editor should save the edited draft in the same file (`$1`) where it read the draft from.
5. If your editor exits with a zero status, whatnow will prompt the user `What now?`. But, as the Section Aborted Draft Messages explains, if your editor exits with a nonzero status, whatnow will abort without sending the message, and:
   - If the mhuse variable is set to 1 (the comp -use program is being used), your draft message won't be deleted.
   - Otherwise, the draft message will be deleted.

distprompter, an editor shell script, acts like prompter to read the message header of a message you're distributing with dist. When it's done reading the header fields, it saves the draft and exits without giving you a chance to type the body (you can't type a body for dist).

Even if you don't run distprompter, it's a good example of what you can do with an MH draft editor. To run distprompter or another editor that you write, put an entry like this in your MH profile:

        dist: -editor distprompter

If you write a more general purpose shell script editor for all the MH message composing programs, you can use an MH profile entry like this instead:

        Editor: myeditor

One more note about editors: even though the mh-profile(5) and whatnow(1) manual pages have a lot of details, they don't explain an editor's environment or the effect of its exit status very thoroughly. I wrote this little test editor script that helped me learn. Maybe it'll help you:

        #! /bin/sh
        echo The environment of $0:
        printenv
        echo "Command line had: '$*'"
        echo -n "Enter exit status for $0: "
        read stat
        exit $stat

Run it by typing, for example:

        % comp -editor testedit