Re: Message-ID's secret

["Adam Sjøgren" <asjo@koldfront.dk>]

황병희 writes:

>>          (message-number-base36 (user-uid) -1))
>
> Sorry still i do not understand what that means.

Let's unpack inside-out:

,----[ C-h f user-uid RET ]
| user-uid is a built-in function in ‘C source code’.
| 
| (user-uid)
| 
|   Probably introduced at or before Emacs version 18.
|   This function does not change global state, including the match data.
| 
| Return the effective uid of Emacs.
| Value is a fixnum, if it’s small enough, otherwise a bignum.
`----

So we get the uid of the user running Emacs. If you're on a one-user
Linux-system, that's often 1000.

For example, on my Debian GNU/Linux machine:

  $ grep $USER /etc/passwd
  asjo:x:1000:1000:Adam Sjøgren,,,:/home/asjo:/bin/bash

my uid is 1000.

Now, the next function:

,----[ C-h f message-number-base36 RET ]
| message-number-base36 is a compiled Lisp function in ‘message.el’.
| 
| (message-number-base36 NUM LEN)
| 
| Not documented.
`----

Not documented, but we can guess what it does from the name - it takes a
number and a length as input, and converts it to base36.

Here is the entire function from message.el:

  (defun message-number-base36 (num len)
    (if (if (< len 0)
            (<= num 0)
          (= len 0))
        ""
      (concat (message-number-base36 (/ num 36) (1- len))
              (char-to-string (aref "zyxwvutsrqponmlkjihgfedcba9876543210"
                                    (% num 36))))))

As 1000 is 27*36 + 28*1, you can see it gets translated into "87" by
this function.

So there is no secret here.

> We can set other user-uid by setq?

No, but if you run Emacs as another user, with another uid, you get
another beginning of your Message-ID.


  Best regards,

    Adam

-- 
 "I wish *I* was a tiger!"                                     Adam Sjøgren
 "A common lament."                                       asjo@koldfront.dk