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bug#22335: 24.2; Documentation of shell-command-on-region incorrect?
From: |
Eli Zaretskii |
Subject: |
bug#22335: 24.2; Documentation of shell-command-on-region incorrect? |
Date: |
Sat, 09 Jan 2016 11:49:18 +0200 |
> Date: Fri, 08 Jan 2016 19:44:11 -0800
> From: Paul Hilfinger <hilfingr@eecs.berkeley.edu>
>
> The current documentation for shell-command-on-region says that
>
> If the optional fourth argument OUTPUT-BUFFER is non-nil,
> that says to put the output in some other buffer.
> If OUTPUT-BUFFER is a buffer or buffer name, put the output there.
> If OUTPUT-BUFFER is not a buffer and not nil,
> insert output in the current buffer.
> In either case, the output is inserted after point (leaving mark after
> it).
>
> If REPLACE, the optional fifth argument, is non-nil, that means insert
> the output in place of text from START to END, putting point and mark
> around it.
>
> This seems to suggest that if REPLACE is nil, the initial contents of
> OUTPUT-BUFFER are retained. However, this does not seem to be the
> behavior of the command at all. Indeed, in the defun for
> shell-command-on-region, there appears:
>
> (if (or replace
> (and output-buffer
> (not (or (bufferp output-buffer) (stringp output-buffer)))))
> ;; Replace specified region with output from command.
> (let ((swap (and replace (< start end))))
> ;; Don't muck with mark unless REPLACE says we should.
> (goto-char start)
> (and replace (push-mark (point) 'nomsg))
> (setq exit-status
> (call-process-region start end shell-file-name t
> (if error-file
> (list t error-file)
> t)
> nil shell-command-switch command))
>
> which would indeed seem to delete the existing text unconditionally.
The argument 't' to call-process-region was changed to 'replace' in
Emacs 24.4, so this appears to be fixed already. I suggest to upgrade
to a newer Emacs version.
Thanks.