Re: Can Emacs pipe a buffer through another one?

[Kevin Rodgers <ihs_4664@yahoo.com>]

J Krugman wrote:
 > In <40D30930.6090309@yahoo.com> Kevin Rodgers <ihs_4664@yahoo.com> writes:
 >>J Krugman wrote:
 >>>Perl at least will let one give it code as the argument to the -e
 >>>flag, which leaves STDIN available for input.  For bash apparently
 >>>something similar holds for the -c flag (but I have no experience
 >>>with it).  I imagine other scripting languages have similar
 >>>mechanisms.  Anyway, as long as the interpreter reads the entire
 >>>script before it executes it (and I don't know of any interpreted
 >>>language for which this isn't the case), then STDIN could serve
 >>>both for feeding the script to the interpreter, and then feeding
 >>>input to the running script[1].  The two tasks do not overlap in time,
 >>>so it should be possible to accommodate both, no?
 >
 >>Cool!
 >>
 >>(with-current-buffer (get-buffer "A")
 >>  (shell-command-on-region (point-min)
 >>                           (point-max)
 >>                           (with-current-buffer (get-buffer "B")
 >>                             (buffer-string))
 >>                           (get-buffer "C")))
 >>
 >
 > You lost me there!  I don't see how this could possibly do what I
 > described.

You want buffer A's contents passed as standard input to the script in
buffer B, with the output going to buffer C.  So:

a. First select buffer buffer A, and pass its contents as standard input
    to a shell command whose output goes to buffer C.

b. The shell command comes from the contents of buffer B, which is
    passed via the -c option to the shell.

`C-h f shell-command-on-region' et al.

 > Can you give me an example of how to use this?

Here's what I did:

1. Create buffer A with `C-x b A', and put some text in it:
one
two
three

2. Create buffer B with `C-x b B', and put a simple script in it:
cd ~; pwd
wc
cd /tmp; pwd

3. Create buffer C with `C-x b C'.  This step could be avoided by using
    (get-buffer-create "C") instead of (get-buffer "C").

4. Copy-and-paste the above form in the *scratch* buffer, and type `C-x
    C-e' or `C-j' (see the "Lisp Interaction" and "Lisp Eval" nodes in
    the Emacs manual).

5. Buffer C now contains:
/home/kevinr
        3       6      28
/tmp

-- 
Kevin Rodgers