How to exit a SET /p in a batch file

Question

How can I exit a SET /p command after a certain time? For instance, if a user takes too long to input something, I want to exit the SET /p.

Answer 1

This is a pure Batch solution that avoid the problems that the Batch-JScript hybrid script have when Sendkeys is used and the original window is not in focus.

@echo off
setlocal EnableDelayedExpansion

rem Execute a SET /P command with time out
rem Antonio Perez Ayala

rem If this file is re-executed as pipe's right side, go to it
if "%~1" equ "TimeoutMonitor" goto %1

del InputLine.txt 2> NUL
(
   set /P "line=You have 10 seconds to complete this input: " > CON
   > InputLine.txt call set /P "=%%line%%" < NUL
) 2> NUL | "%~F0" TimeoutMonitor 10
set /P "line=" < InputLine.txt
del InputLine.txt
echo Line read: "!line!"
goto :EOF


:TimeoutMonitor

rem Get the PID of pipe's left side
tasklist /FI "IMAGENAME eq cmd.exe" /FO TABLE /NH > tasklist.txt
for /F "tokens=2" %%a in (tasklist.txt) do (
   set "leftSidePipePID=!lastButOnePID!"
   set "lastButOnePID=%%a"
)
del tasklist.txt

rem Wait for the input line, or until the number of seconds passed
for /L %%i in (1,1,%2) do (
   ping -n 2 localhost > NUL
   if exist InputLine.txt exit /B
)

rem Timed out: kill the SET /P process and create a standard input line
taskkill /PID %leftSidePipePID% /F > NUL
echo/
echo Timed Out> InputLine.txt

exit /B

Answer 2

Essentially, you can't.

You may be able to use choice to accept a single character with timeout.