http://support.microsoft.com/?kbid=135268Says:
The CACLS.EXE command line utility does not provide a /Y switch that automatically answers with Y for Yes to the ARE YOU SURE? Y/N prompt. However, you can use the echo command to pipe the character Y as input to the ARE YOU SURE? Y/N prompt when you call Cacls.exe in a batch file.
To programmatically answer with Yes to the ARE YOU SURE? Y/N prompt during batch file execution, use the following command line in your batch file:
echo y| cacls filename /g username:permission
NOTE: Do not type a space between the "y" and the pipe symbol (|), otherwise, Cacls.exe fails to make the permission changes.
In larger batch files, this may produce the following error before continuing to the next line:
The Process tried to write to a nonexistent pipe.
The echo command does not expel its output before the system has a chance to build the pipe to cacls. There are different ways to work around this.
As an alternative, you can create a dummy file with just a "y" in it and use the syntax:
Cacls "F:\Directory" /g "Domain Users":R < yes.txt
Or you can use the xcacls utility which does allow the /y:
xcacls "F:\Directory" /e /g "Domain Users":R /y