bug#4408: 23.1; suggestion: a elisp function for copying and deleting whole dir

bug#4408: 23.1; suggestion: a elisp function for copying and deleting whole dir

[Xah Lee]

it appears to me, this is a good suggestion.

there lacks a function to copy and delete directories recursively.

in the elisp manual, the closest is:
(info "(elisp) Create/Delete Dirs")

it would be good to have a function that copy a whole dir, and another for 
deleting whole dir.

Emacs does implement them in dired, or in eshell, apparently, but it's not 
easy to use them.

many scripting langs provide such functions, and is very convenient.

for deleting dir, perhaps this can be implemented:
(delete-directory dirname &optional recursive)

for copying dir, perhaps it can be modeled on copy-file:
 -- Command: copy-file oldname newname &optional ok-if-exists time

these should be perhaps few hours to implement for elisp developers, perhaps 
by just pulling existing implementation from dired or eshell.

Once implemented, they'd be standard functions in elisp manual. They would 
be great convience for average elisp coders.

As a personal example, i needed to both copy dir recursively and also delete 
whole dir, in my use of elisp as a text processing lang. So far i've been 
just calling shell. e.g.
(shell-command (concat "cp -R " fromDir " " toDir))
(shell-command (concat "find " destDir " -type d -name \"xx*\" -exec rm -R 
{} \\;"))

my script worked well in the past 2 years, but replying on unix shell has 
many complications. For example, recently i need my script to work on 
Windows. With Windows, there's many complications, e.g. which unix shell you 
use cygwin, msys, their config, their path env var config in emacs, both are 
inter-related to which emacs distribution one is using (e.g. what shell runs 
when you do M-x shell). Then, recently in one emacs distro i'm trying out 
eshell (in hope that it perhaps more cross-platform than M-x shell or 
Lennart emacsW23's shell, cmd-shell, msys-shell), but discovered that eshell 
chocks on this standard bash syntax
find -name "*el" -exec rm {} \;
(reported in bug #4406. Doesn't work when called as shell-command neither)

In short, something trivial turns out to be 5 or more hours to trying to get 
it work.

emacs + elisp is a great text processing lang, and one big advantage is that 
it is cross platform. So, all things considered, i think the suggestion in 
this report is a very good one, in particular its ratio of 
impact/ease-to-implement is relatively high.

if i eventually got a solution from looking into dired or eshell for 
copying/deleting dir, i'll update this report with code for draft 
implementation.

Thanks.

  Xah
∑ http://xahlee.org/

☄