title: how to clear a variable which is set from command line by "set /p var1="
body: <p>In Windows batch files, I accept variable from user input by <code>set /p var1=</code>, after <code>var1</code> is used, I don't know how to reset/clear its value. </p>
  
  <p>If I don't reset/clear its value, when user meets <code>set /p var1=</code> again, and user enter directly. the previous input value will be still there. I don't want it, How to reset it for new user input?</p>