Create process and pipe buffer to process as input
reddit / emacs

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Tohiko · 2022-04-27 14:49

When using the functions `make-process` or `start-process`, is there a
way to pipe the content of a buffer as input to the created process? I
need this especially for temporary buffers that do not have a file (I
know that I can create a temporary file, but I would like to avoid
this if possible).

I couldn't find a way to do so. Even in eshell, when I try something
like `cmd < #<buffer>` I get `Eshell does not support input
redirection`.

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h-m-b-tu · 2022-04-27 14:54

You can pass `make-process` the option `:connection-type 'pipe` and
then use `process-send-string` to pass input to the process. Use
`process-send-eof` to close the pipe.

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rpluim · 2022-04-27 15:45

Does it have to use `make-process` or `start-process`? Because there's
`shell-command-on-region` or the underlying `call-process-region`

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globalcandyamnesia · 2022-04-27 16:30

(call-process-region (point-min) (point-max) "cat" nil t)

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Tohiko · 2022-04-27 16:36

Brilliant!

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Tohiko · 2022-04-27 16:37

These two functions create synchronous process as far as I can see,
right? I need my process to be asynchronous.

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nanounanue · 2022-04-28 02:44

Emacslisp noob  here, mind to share the full code?

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h-m-b-tu · 2022-04-28 09:19

Here as an example:

``` elisp
(let ((process (make-process :name "process name"
                             :buffer nil ;; no buffer for process
output
                             :command (list "executable" "argument_1"
"argument_2" "..." "argument_n")
                             :connection-type 'pipe)))
  (process-send-string process "string to pipe to process")
  (process-send-eof process)             ;; close pipe
  )
```

See also the documentation of `make-process`.