No args Display help. This is the same as typing /?.
/? Display help. This is the same as not typing any options.
/i Display the graphical user interface (GUI).
This must be the first option.
/l Log off. This cannot be used with /m or /d options.
/s Shutdown the computer.
/r Shutdown and restart the computer.
/g Shutdown and restart the computer. After the system is
rebooted, restart any registered applications.
/a Abort a system shutdown.
This can only be used during the time-out period.
/p Turn off the local computer with no time-out or warning.
Can be used with /d and /f options.
/h Hibernate the local computer.
Can be used with the /f option.
/e Document the reason for an unexpected shutdown of a computer.
/m \\computer Specify the target computer.
/t xxx Set the time-out period before shutdown to xxx seconds.
The valid range is 0-315360000 (10 years), with a default of 30.
If the timeout period is greater than 0, the /f parameter is
/c "comment" Comment on the reason for the restart or shutdown.
Maximum of 512 characters allowed.
/f Force running applications to close without forewarning users.
The /f parameter is implied when a value greater than 0 is
specified for the /t parameter.
/d [p|u:]xx:yy Provide the reason for the restart or shutdown.
p indicates that the restart or shutdown is planned.
u indicates that the reason is user defined.
If neither p nor u is specified the restart or shutdown is
xx is the major reason number (positive integer less than 256).
yy is the minor reason number (positive integer less than 65536).
/a are the options of interest here.
/t provides a timeout
/a allows a user to cancel a shutdown process while waiting for timeout
/c allows you to supply a message (
/d affects the logs)
Possible solution - In the comment, state that the shutdown can be cancelled by running
shutdown /a within the timeout.
Do consider email to users describing this in more detail.
Another solution would be to run a short script that gives the user the option of postponing or authorising the shutdown, at which point it would wait, or run the shutdown command.
Edit: Found pretty much the same question on SO, answered here:
A batch file for shutdown with prompt option to abort it and re-run after a certain time of amount?