Lua-System docs

## spinner.lua

    local sys = require("system")

    print [[

    An example to display a spinner, whilst a long running task executes.

    ]]

    -- start make backup, to auto-restore on exit
    sys.autotermrestore()
    -- configure console
    sys.setconsoleflags(io.stdin, sys.getconsoleflags(io.stdin) - sys.CIF_ECHO_INPUT - sys.CIF_LINE_INPUT)
    local of = sys.tcgetattr(io.stdin)
    sys.tcsetattr(io.stdin, sys.TCSANOW, { lflag = of.lflag - sys.L_ICANON - sys.L_ECHO })
    sys.setnonblock(io.stdin, true)

    local function hideCursor()
      io.write("\27[?25l")
      io.flush()
    end

    local function showCursor()
      io.write("\27[?25h")
      io.flush()
    end

    local function left(n)
      io.write("\27[",n or 1,"D")
      io.flush()
    end

    local spinner do
      local spin = [[|/-\]]
      local i = 1
      spinner = function()
        hideCursor()
        io.write(spin:sub(i, i))
        left()
        i = i + 1
        if i > #spin then i = 1 end

        if sys.readkey(0) ~= nil then
          while sys.readkey(0) ~= nil do end -- consume keys pressed
          io.write(" ");
          left()
          showCursor()
          return true
        else
          return false
        end
      end
    end

    io.stdout:write("press any key to stop the spinner... ")
    while not spinner() do
      sys.sleep(0.1)
    end

    print("Done!")

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