RE: display-time-string-forms

["Drew Adams" <drew.adams@oracle.com>]

> >> I have  
> >>   (setq display-time-format "%R %Y-%m-%d")
> >> which gives me
> >>       08:47 2007-10-10
> >> in the mode line.
> > 
> > What steps do you take to get the time to appear in  your 
> > modeline? I've messed with this and _never_ been able to get
> > the time to appear in mine.
> 
> From menu:
> Options
> Customize Emacs
> Specific options
> display TAB
> 
> Then setting 2 of these options should put
> '(display-time-day-and-date t)
>   '(display-time-mode t nil (time))
> 
> into your .emacs custom-set-variables section.
> There is also the function
>   display-time-string-forms
> with which I haven't messed.
> 
> Btw, this is in version 21.3. Newer versions certainly have the same 
> functionality.

Icicles can help you _find_ what you might need to customize:

M-x icicle-vardoc RET .* C-q C-g C-j .*time S-SPC .*mode[- ]line

This shows, as completion candidates, all variables, with their doc strings, for which all of the following are true:

* the variable name matches anything: .*
* the doc string contains "time": .*time
* the doc string also contains either "mode-line" or "mode line":
  .*mode[- ]line

The order in the doc string of "time" and "mode-line" (or "mode line") does not matter - all possible orders are considered when you use `S-SPC'.

The incantation C-q C-g C-j just matches the separator used between variable name and doc string, for each completion candidate. The default separator is C-g C-j, and C-q is used to quote the C-q character. (In Icicles, C-j is self-inserting and does not need to be quoted.)

This quickly shows you the following completion candidates (in *Completions*):

 appt-display-mode-line
 *Non-nil means display minutes to appointment and time on the mode line.
 This is in addition to any other display of appointment messages.
--
 display-time-format
 *String specifying format for displaying the time in the mode line.
 See the function `format-time-string' for an explanation of
 how to write this string.  If this is nil, the defaults
 depend on `display-time-day-and-date' and `display-time-24hr-format'.
--
 display-time-hook
 *List of functions to be called when the time is updated on the mode line.
--
 display-time-interval
 *Seconds between updates of time in the mode line.
--
 display-time-string-forms
 *List of expressions governing display of the time in the mode line.
 For most purposes, you can control the time format using `display-time-format'
 which is a more standard interface.

 This expression is a list of expressions that can involve the keywords
 `load', `day', `month', and `year', `12-hours', `24-hours', `minutes',
 `seconds', all numbers in string form, and `monthname', `dayname', `am-pm',
 and `time-zone' all alphabetic strings, and `mail' a true/nil value.

 For example, the form

  '((substring year -2) "/" month "/" day
    " " 24-hours ":" minutes ":" seconds
    (if time-zone " (") time-zone (if time-zone ")")
    (if mail " Mail" ""))

 would give mode line times like `94/12/30 21:07:48 (UTC)'.
--

You can further reduce the number of candidates by filtering with one or more additional patterns (e.g. S-SPC format).

Even more generally, you can look at all functions and all variables whose doc strings contain the strings "time" and either "mode-line" or "mode line":

M-x icicle-doc RET time S-SPC mode[- ]line

That shows, as completion candidates, the doc strings of all functions and all variables that contain both "time" and either "mode-line" or "mode line", in either order. Click `mouse-2' on any candidate to see it (including the function or variable name) displayed in *Help*. Again, you can use additional patterns to further reduce the number of hits.