(defun shell-command-on-region-replace (start end command)
"Run shell-command-on-region interactivly replacing the region in place"
(interactive (let (string)
(unless (mark)
(error "The mark is not set now, so there is no region"))
;; Do this before calling region-beginning
;; and region-end, in case subprocess output
;; relocates them while we are in the minibuffer.
;; call-interactively recognizes region-beginning and
;; region-end specially, leaving them in the history.
(setq string (read-from-minibuffer "Shell command on region: "
nil nil nil
'shell-command-history))
(list (region-beginning) (region-end)
string)))
(shell-command-on-region start end command t t)
)
(defun generalized-shell-command (command arg)
"Unifies `shell-command' and `shell-command-on-region'. If no region is
selected, run a shell command just like M-x shell-command (M-!). If
no region is selected and an argument is a passed, run a shell command
and place its output after the mark as in C-u M-x `shell-command' (C-u
M-!). If a region is selected pass the text of that region to the
shell and replace the text in that region with the output of the shell
command as in C-u M-x `shell-command-on-region' (C-u M-|). If a region
is selected AND an argument is passed (via C-u) send output to another
buffer instead of replacing the text in region."
(interactive (list (read-from-minibuffer "Shell command: " nil nil nil 'shell-command-history)
current-prefix-arg))
(let ((p (if mark-active (region-beginning) 0))
(m (if mark-active (region-end) 0)))
(if (= p m)
;; No active region
(if (eq arg nil)
(shell-command command)
(shell-command command t))
;; Active region
(if (eq arg nil)
(shell-command-on-region p m command t t)
(shell-command-on-region p m command)))))