How do I loop a program that waits for a .dat file to be updated?

I am trying to loop a program that calls data from a gui input.

In this case 'steps.dat' is created from a gui input and everytime the input changes so does the .dat file. Now I need to loop this program so that everytime the input changes the program runs, but i dont want it to run endlessly i want it to wait for the .dat file to be changed.

Thank you

while 
    F=load('steps.dat')

   for motornum= 1:3
    direc= sign(F(motornum))
    steps=abs(F(motornum))
   end

end

[Luna]

what kind of gui element you are using to get your .dat file?

[Sam Soifer]

The gui Is a forward/ inverse kinematic solution that calculates the number of steps for 3 diffirent motors to move. This command will than be sent to arduino.

[Luna]

Your gui element means when you import your .dat file to your gui by using a browse button, etc.

Define a callback function for that uicontrol object then you can do what ever you want, each time you clicked the button matlab calls the callback function.

Answer 1

[Mark Sherstan]

Depending on the size of your .dat file this may work for your application:

while 
   while ~isfile('steps.dat'); end
   
   F = load('steps.dat');
   
   for motornum = 1:3
    direc = sign(F(motornum));
    steps = abs(F(motornum));
   end
   
   delete steps.dat
end

[Sam Soifer]

my .dat file is a 3x1 matrix. When I try this i get an error

"Invalid expression. Check for missing or extra characters."

[Mark Sherstan]

Sorry I mis read / mis understood part of your question. This should now work:

while 1
    
   while 1
        if isfile('steps.dat') == 1
            F = load('steps.dat');
            break
        end
   end
   
   for motornum = 1:3
        direc = sign(F(motornum));
        steps = abs(F(motornum));
   end
   
   delete steps.dat
end

Please let me know if it works!

[Sam Soifer]

The code never makes it to the for loop

[Mark Sherstan]

Something from your GUI writing the file isent being initialized then. It worked for me when I dragged the file into the directory.

[Sam Soifer]

This is the line of code from my GUI that I am using to write the .dat file

save('steps.dat','FxStep','FyStep','FzStep','-ascii')