emacs/openwith how to pass arguments to program?

Question

I am using the openwith package in emacs. I would like to open .fig files with xfig with some additional options, for example:

xfig -specialtext -latexfont -startlatexFont default file.fig

openwith is working for me with other file associations where I don't need to pass additional options. I tried the following in my .emacs file

(setq
 openwith-associations 
 '(("\\.fig\\'" "xfig" (file))))

which works, but

(setq
 openwith-associations 
 '(("\\.fig\\'" "xfig -specialtext -latexfont -startlatexFont default" (file))))

does not work (error: Wrong type argument: arrayp, nil), also

(setq
 openwith-associations 
 '(("\\.fig\\'" "xfig" (" -specialtext -latexfont -startlatexFont default " file))))

does not work, although here I don't get any error. It says "Opened file.fig in external program" but nothing happens. In this case, I notice that there is an xfig process running with all these options.

Could someone let me know how to fix this?

Thanks for the help.

whoplisp · Accepted Answer · 2011-07-30T20:25:39.957

I have no clue how this works, so I just document how one can figure it by reading the code:

The important code in openwith.el is the call to start-process in:

(dolist (oa openwith-associations)
  (let (match)
    (save-match-data
      (setq match (string-match (car oa) (car args))))
    (when match
      (let ((params (mapcar (lambda (x)
                  (if (eq x 'file)
                  (car args)
                  (format "%s" x))) (nth 2 oa))))
    (apply #'start-process "openwith-process" nil
           (cadr oa) params))
      (kill-buffer nil)
      (throw 'openwith-done t))))

The in your case oa would have the following structure, and the cadr is "xfig":

(cadr '("\.fig\'" "xfig" (file))) ;; expands to => xfig

This is the definition and doc of start-process:

Function: start-process name buffer-or-name program &rest args http://www.gnu.org/software/emacs/elisp/html_node/Asynchronous-Processes.html

 args, are strings that specify command line arguments for the program.

An example:

(start-process "my-process" "foo" "ls" "-l" "/user/lewis/bin")

Now we need to figure out how params is constructed. With your example the argument to the mapcar is:

(nth 2 '("\.fig\'" "xfig" (file))) ;=> (file)

By the way you can write such lines in the scratch buffer in emacs and run them with C-M-x.

The (car args) refers to the parameter you give to openwith-association, note how the occurance of 'file in (nth 2 oa) is replaced by that. I'll just replace it with "here.txt" for now:

(mapcar (lambda (x)
      (if (eq x 'file)
          "here.txt"
          (format "%s" x))) (nth 2 '("\.fig\'" "xfig" (file)))) ;=> ("here.txt")

Okay, now we see how the argument should be constructed:

(mapcar (lambda (x)
      (if (eq x 'file)
          "here.txt"
          (format "%s" x))) 
    (nth 2 '("\.fig\'" "xfig" 
         ("-specialtext" "-latexfont" "-startlatexFont" "default" file))))
; => ("-specialtext" "-latexfont" "-startlatexFont" "default" "here.txt")

Try this:

(setq openwith-associations 
 '(("\\.fig\\'" "xfig" ("-specialtext" "-latexfont" "-startlatexFont" "default" file))))

You have to supply each word as a single string in the list of parameters.

Note that Noufal Ibrahim edited (correctly, as the strings in openwith.el always have two backslashes) the slashes in your question. The last example in my answer should be correct. — whoplisp, Jul 30 '11 at 20:19

emacs/openwith how to pass arguments to program?

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