Emacs DWIM shell-command

I've drawn inspiration from dired-do-shell-command, which substitutes special characters like * and ? with marked files. I'm also drawing inspiration from org babel's noweb syntax to substitute <<f>> (file path), <<fne>> (file path without extension), and <<e>> (extension). My initial preference was to use something like $f, $fne, and $e, but felt they clashed with shell variables.

This is DWIM, so if we're visiting a dired buffer, the shell command should operate on all the marked files.

Similarly, if visiting a buffer with an associated file, operate on that file instead.

Did the command create a new file in the current directory? Take me to it, right away.

I'm not usually interested in the command output when generating new files, unless there was an error of course. Offer to show it.

Not all commands generate new files, so automatically show me the output for these instances.

ffmpeg is awesome, but man I can never remember all the flags and arguments. I may as well wrap commands like these in a convenient elisp function and invoke via execute-extended-command, or my favorite counsel-M-x (with completion), bound to the vital M-x.

All those gifs you see in this post were created with dwim-shell-command-convert-to-gif, powered by the same elisp magic.

(defun dwim-shell-command-convert-to-gif ()
  "Convert all marked videos to optimized gif(s)."
  (interactive)
  (dwim-shell-command--on-marked-files
   "ffmpeg -loglevel quiet -stats -y -i <<f>> -pix_fmt rgb24 -r 15 <<fne>>.gif"
   "Convert to gif" '("ffmpeg")))

This makes wrapping one-liners a breeze, so let's do some more…

(defun dwim-shell-command-convert-audio-to-mp3 ()
  "Convert all marked audio to mp3(s)."
  (interactive)
  (dwim-shell-command--on-marked-files
   "ffmpeg -stats -n -i <<f>> -acodec libmp3lame <<fne>>.mp3"
   "Convert to mp3" '("ffmpeg")))

(defun dwim-shell-command-convert-image-to-jpg ()
  "Convert all marked images to jpg(s)."
  (interactive)
  (dwim-shell-command--on-marked-files
   "convert -verbose <<f>> <<fne>>.jpg"
   "Convert to jpg" '("convert")))

(defun dwim-shell-command-drop-video-audio ()
  "Drop audio from all marked videos."
  (interactive)
  (dwim-shell-command--on-marked-files
   "ffmpeg -i <<f>> -c copy -an <<fne>>_no_audio.<<e>>"
   "Drop audio" '("ffmpeg")))

Ok, not quite, but use Emacs's progress-reporter just for kicks.