How to provide quoted parameters to System.cmd

kokolegorille

Hello everyone,

I am trying to run image magick convert from Elixir. The command I am trying to replicate is…

$ convert -size 200x200 xc:Black -fill White -draw 'circle 100 100 100 1' -alpha Copy mask.png

Which is working fine in the shell. It generates a new image correctly.

And now I am trying to do this in the BEAM.

  def build_mask(size) do
    params = [
      "-size",
      "#{size}x#{size}",
      "xc:Black",
      "-fill",
      "White",
      "-draw",
      "'circle 100 100 100 1'",
      "-alpha",
      "Copy",
      "mask.png"
    ]
    System.cmd(convert(), params)
  end

  defp convert() do
    case System.cmd("which", ["convert"]) do
      {convert_cmd, 0} -> String.trim_trailing(convert_cmd, "\n")
      {_, 1} -> ""
    end
  end

which fails with

convert: non-conforming drawing primitive definition `circle 100 100 100 1' @ error/draw.c/RenderMVGContent/4397.

The problem is in these lines, if I comment them, the command is working.

"-draw",
"'circle 100 100 100 1'",

So my question is how to pass a quoted parameters like this ‘circle 100 100 100 1’.

I have been trying different combination, with escape, double quote and what not.

Does anybody hit the same problem trying to wrap convert command in the BEAM?

Thanks for taking time

7 comments

#elixir

0 2098 7

2022-03-11 19:43:00 UTC

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NobbZ

The quotes are a shell thing, just leave them off and just use "circle 100 100 100 1".

Post #1

kokolegorille

Oh my… it is now working fine

Post #2

sergio

I’m running into a similar issue trying to run wkhtmltopdf with a string HTML.

    html_string =
      Phoenix.View.render_to_string(FooWeb.PdfView, "contract.html",
        test_name: "Brawl Smash Bros."
      )

    download_folder = Application.app_dir(:myapp, ["priv", "static", "pdfs"])
    pdf_save_path = "#{download_folder}/contract.pdf"

    IO.inspect("wkhtmltopdf " <> html_string <> " " <> pdf_save_path)

    System.cmd("wkhtmltopdf", [html_string, pdf_save_path])

Result:

iex [16] > myapp.Pdf.generate_team_contract()
"wkhtmltopdf <h1>This is your team contract</h1>\n\n<p>You are playing in Brawl Smash Bros.</p> /home/sergio/Work/myapp/_build/dev/lib/myapp/priv/static/pdfs/team-contract.pdf"
Loading pages (1/6)
Error: Failed to load http:/p>, with network status code 3 and http status code 0 - Host  not found
                                                                                                   Error: Failed loading page http:/h1>

                  <p>You are playing in Brawl Smash Bros.</p> (sometimes it will work just to ignore this error with --load-error-handling ignore)
                             Exit with code 1 due to network error: HostNotFoundError
                                                                                     {"", 1}

Anyone have any tips on how to run this command? The HTML isn’t being quoted.

Post #3

al2o3cr

I don’t see any mention of passing HTML directly via the command line in the wkhtmltopdf docs, escaped or otherwise.

Post #4

03juan

wkhtmltopdf expects a URL or file. You’ll have to File.write(tmp_html_path, html_string) and System.cmd("wkhtmltopdf", [tmp_html_path, pdf_save_path])

Post #5