Creating tool license function

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adi kul 2018-2-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/385140-creating-tool-license-function

编辑： Guillaume 2018-2-28

Hi, I have created a basic tool to calculate few of the formulas which I was working on. Now I have converted into a simple script and want to put a license kind of function which will show "license expired" error upon exceeding the date.

this so far I could put together: in Tool_validity i have:

function Tool_validity
    if now > datenum('2018-01-01') % this code stops working Jan 1, 2018
    disp('Please update your License') ;
    return
  end

and in my script I have put:

Tool_validity;

Thing is, after the message, the tool still proceeds to next steps. I don't want it to proceed further. Please let me know how can I make it work.

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Guillaume 2018-2-27

Sure. But the user could also just replace the default now.m (in my version, under C:\Program Files\MATLAB\R2017b\toolbox\matlab\timefun\now.m) by their own to once again work around the license check.

My point is that sort of license checks are extremely fragile and won't stop much.

Rik 2018-2-27

You could also either hard-code the implementation of now (so t=datenum(builtin('clock'));), or get the time from the internet.

But even if you do, your m-file can be changed, p-code can be decompiled (and reduces the number of releases that will run your code), and time servers can be spoofed. It is always an arms race. Every creator will almost always be on the losing end.

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采纳的回答

Guillaume 2018-2-27

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在 MATLAB Online 中打开

Well, yes disp only displays the message then proceeds with the next line. error aborts the code:

 if now > datenum('2018-01-01') % this code stops working Jan 1, 2018
    error('Please update your License') ;
 end

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Guillaume 2018-2-27

编辑：Guillaume 2018-2-28

在 MATLAB Online 中打开

The only way to stop code executing in matlab is with the error function (or with debug commands but that's certainly not what you want). Unfortunately, in matlab there is no way to stop error from displaying the call stack, so yes it may display a lot of red text.

The only other option is for your license check function to return a flag that is propagated back to the main function/script which would immediately return if the flag is set.

   %main code:
   %...
   isvalid = validate_license;
   if ~isvalid
      fprintf(2, 'License outdated. Please update);  %fprintf(2, ...) to output in red
      return;  %quit main code
   end
   %continue since license is valid
   %...
function isvalid = validate_license
    isvalid = now <= datenum('2018-01-01')
end