M-x call with optional arg; call from Elisp

M-x call with optional arg; call from Elisp

[Emanuel Berg]

Take a look at the below code, and you'll understand immediately what
I ask.

1. How can I call a function with M-x and provide an optional string
arg?

2. Why do I get 0 when I call from Elisp? (Is it the return code - $?
- and not the output?) I tried with eval and funcall as well:
same. How do I call from Elisp?

;;; word count
(defun words (&optional opts)
  "Count buffer words with wc OPTS, or wc -w if not OPTS is given."
  (interactive)
  (defvar count-cmd)
  (setq count-cmd (format "wc %s" (if (stringp opts) opts "-w")))
  (if mark-active
    (shell-command-on-region (region-beginning) (region-end) count-cmd)
    (shell-command-on-region (point-min) (point-max) count-cmd) ))
(words "-l") ; doesn't work (0) - can I call this with M-x and an arg?
(words)      ; same, but `M-x words' works

(defun count-buffer-wc-option (option)
  (interactive "s wc options: ")
  "Count buffer according to wc OPTION."
  (shell-command-on-region (point-min) (point-max)
                           (format "wc %s" option)) )
(count-buffer-wc-option "-l") ; same, but
                              ; `M-x count-... RET -l' works

-- 
Emanuel Berg - programmer (hire me! CV below)
computer projects: http://user.it.uu.se/~embe8573
internet activity: http://home.student.uu.se/embe8573

Re: M-x call with optional arg; call from Elisp

[Emanuel Berg]

Emanuel Berg <embe8573@student.uu.se> writes:

> (defun count-buffer-wc-option (option)
>   (interactive "s wc options: ")
>   "Count buffer according to wc OPTION."
>   (shell-command-on-region (point-min) (point-max)
>                            (format "wc %s" option)) )

Oh, I should say not to cause confusion, the above function - I only
wrote it for test purposes - if I get the other function to work,
that should cover both.

-- 
Emanuel Berg - programmer (hire me! CV below)
computer projects: http://user.it.uu.se/~embe8573
internet activity: http://home.student.uu.se/embe8573

Re: M-x call with optional arg; call from Elisp

[Stefan Monnier]

> 1. How can I call a function with M-x and provide an optional string
> arg?

You have to put in the `interactive' spec a description of what value
to pass.

> 2. Why do I get 0 when I call from Elisp?

Because that's the value of the last expression.

> (Is it the return code - $? - and not the output?)

Yes.

>   (defvar count-cmd)
>   (setq count-cmd (format "wc %s" (if (stringp opts) opts "-w")))

`defvar does not define the variable, nor declares it as local.
Quite the opposite, it basically declares it as global (or rather as
dynamically-scoped, which ends up being fairly close).
You want to use

  (let ((count-cmd (format "wc %s" (if (stringp opts) opts "-w"))))

instead.

>   (if mark-active
>     (shell-command-on-region (region-beginning) (region-end) count-cmd)
>     (shell-command-on-region (point-min) (point-max) count-cmd) ))

Don't use shell-command-on-region from Elisp.  Use call-process-region instead.


        Stefan

Re: M-x call with optional arg; call from Elisp

[Emanuel Berg]

First, I got this reply as a mail, but I don't see it on the list.

Quoting "B. T. Raven":

> As in your "count-buffer-wc-option" function below. Of course the
> whole exercise can be avoided with M-| or C-x h M-|

`C-x h' would be mark-whole-buffer, and M-| (pipe)
shell-command-on-region. Tough that is certainly an alternative, I
think `M-x words' is a lot better (on the region if there is one;
otherwise, the entire buffer). So this is not an "exercise", I set it
up because I intend to use it.

> Since a null string is still a string you need something like
> (length opts).

My thought was rather - it is not even a null string if no optional
arg is passed. I don't know if that is the case; but that would be
easy to find out once I'm able to call the functions as intended,
with or without the optional arg.

-- 
Emanuel Berg - programmer (hire me! CV below)
computer projects: http://user.it.uu.se/~embe8573
internet activity: http://home.student.uu.se/embe8573

Re: M-x call with optional arg; call from Elisp

[Emanuel Berg]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> 1. How can I call a function with M-x and provide an optional
>> string arg?
>
> You have to put in the `interactive' spec a description of what
> value to pass.

Yes, that did it: this works from M-x:

(defun words (&optional opts)
  "Count buffer words with wc OPTS, or wc -w if not OPTS is given."
  (interactive "s (RET for -w) options to wc: ")
  (let*((options (if (not (string= "" opts)) opts "-w"))
        (count-cmd (format "wc %s" options)) )
   (if mark-active
    (shell-command-on-region (region-beginning) (region-end) count-cmd)
    (shell-command-on-region (point-min) (point-max) count-cmd) )))

> defvar does not define the variable, nor declares it as local.
> Quite the opposite, it basically declares it as global (or rather
> as dynamically-scoped, which ends up being fairly close). You want
> to use let.

Aha, when I started with Elisp, I always used let, but then I found
defvar and started using it, because the syntax is much easier to
use. I thought defvar gave a local variable if in a defun.

> Don't use shell-command-on-region from Elisp. Use
> call-process-region instead.

The above function seems to work. shell-command-on-region and
call-process-region are not syntactically interchangeable, but I'll
do it if you care to tell me the advantage.
-- 
Emanuel Berg - programmer (hire me! CV below)
computer projects: http://user.it.uu.se/~embe8573
internet activity: http://home.student.uu.se/embe8573

Re: M-x call with optional arg; call from Elisp

[Kevin Rodgers]

On 5/28/13 1:52 PM, Emanuel Berg wrote:
> Stefan Monnier<monnier@iro.umontreal.ca>  writes:
>> Don't use shell-command-on-region from Elisp. Use
>> call-process-region instead.
>
> The above function seems to work. shell-command-on-region and
> call-process-region are not syntactically interchangeable, but I'll
> do it if you care to tell me the advantage.

If you are not using shell features such as redirection, pipes, globbing (file
name expansion), variable expansion, conditional and iterative control flow
etc. then there is no need to invoke an additional/intermediary shell process
between emacs and the command you want to run.

-- 
Kevin Rodgers
Denver, Colorado, USA