Help with process filters
reddit / emacs

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Substantial_Quit_481 · 2022-08-20 05:49

I often start processes which print their progress on a terminal, but
the output gets printed messily in the process buffer. For example

    Reading track 1 of 4 (1 of 9) ...   0 %^MReading track 1 of 4 (1
of 9) ...   1 %^MReading track 1 of 4 (1 of 9) ...   2 %^MReading
track 1 of 4 (1 of 9) ...   3 %

Where the `^M` is a newline character, I guess.

How could I print progress like it does on a terminal into the process
buffer, overwriting the previous % and respecting newlines? I have
looked at process filters but cannot understand how I would write one.

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xenodium · 2022-08-20 08:01

shell-mode in the process buffer may help:

    (with-current-buffer proc-buffer
      (require 'shell)
      (shell-mode))

and set filter to `comint-output-filter`.

ps. You can see colors in buffer in some of the sample animations
https://github.com/xenodium/dwim-shell-command#focus using the above.

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eli-zaretskii · 2022-08-20 08:03

You need to process the ^M characters by erasing everything before it.

(There are now newlines in the process output: it relies on the ^M to
home the cursor on the terminal.)

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7890yuiop · 2022-08-20 10:52

`^M` (ASCII 13) is a carriage return, rather than a newline.  (A
newline character is ASCII 10, `^J`.)

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Substantial_Quit_481 · 2022-08-20 14:49

This works perfectly, thanks!