Batch choice alternative for detecting key without pause - batch-file

Question

The question is: is here any way to detect keypress in batch without pausing entire script for scripts like chat, games etc? For now I know about useful command called xcopy. I use it to detect and extract pressed key such as Enter. But it pauses entire script and waits for confirmation, while chose may not pause script, but unable to do silent invalid key as well as detecting specific ones

Answer 1

It's not simple with pure batch, but possible.
This is a sample that uses two threads.
The first thread :keyCheck waits for a key.
The second thread :mainFunc counts until a key is pressed.
#echo off
setlocal DisableDelayedExpansion
set "func=%~0"
for /F "delims=\" %%X in ("%func:*\=%") do set "func=%%X"
if ":" == "%func:~0,1%" (
goto %func%
)
( "%~d0\:keyCheck\..%~pnx0" ) > lock.tmp | "%~d0\:mainFunc\..%~pnx0"
echo Ende
exit /b
REM *** Thread1 - waiting for key
:keyCheck
for /f skip^=1^ delims^=^ eol^= %%A in ('replace.exe ? . /u /w') do for /f delims^=^ eol^= %%B in ("%%A") do (
set key=%%B
)
exit /b
REM *** Thread2 - Counting up
:mainFunc
setlocal EnableDelayedExpansion
for /F %%# in ('copy /Z "%~dpf0" NUL') do set "CR=%%#"
set "lastTime="
set cnt=0
:loop
set /a cnt+=1
set /p "=Stop with any key !cnt! !CR!" < nul
call :waitOrStop
goto :loop
:waitOrStop
REM Check if a key was pressed, then the lock is released
(
(
rem
) 2> lock.tmp && (
echo(
exit
)
) 2> nul
set "now=%time:~-2%"
if "!now!" NEQ "!lastTime!" (
set "lastTime=!now!"
exit /b
)
goto :waitOrStop

Answer 2

While it is not at all straightforward, the site Dostips.com has a full implementation of the game "Snake" using nothing but Batch, including non-blocking input.
Essentially, the batchfile spawns a second command prompt, which is blocking on input. When input is received, it is routed to the first, "main" program which polls the input file.
Like I said, not straightforward or simple, but it is do-able.

Answer 3

Although possible, there is not a simple way to do that using pure Batch commands. The simplest way is use a third party .exe program specifically designed to do so, like my GetKey.exe auxiliary file. This program get a key from keyboard and returns via ERRORLEVEL a value that indicate the key pressed. All keys are processed: ASCII characters are returned as positive values and extended keys (function keys, cursor control keys, etc) as negative values. If /N switch is given, GetKey.exe no waits: if a key was not pressed the value returned is zero.
This is a very simple example program that use GetKey.exe auxiliary file:
#echo off
setlocal EnableDelayedExpansion
rem Simple example of GetKey.exe auxiliary program to detect keys pressed
rem Get a Return (ASCII 13) CR character
for /F %%a in ('copy /Z "%~F0" NUL') do set "CR=%%a"
cls
echo Press a key at any moment; press ESC key to end
echo/
set i=0
:loop
set /A i+=1
set /P "=%i%!CR!" < NUL
GetKey /N
if %errorlevel% equ 0 goto loop
echo/
echo Key pressed: %errorlevel%
if %errorlevel% neq 27 goto loop
You may download GetKey.exe auxiliary program from this site; you may also download SHOWKEYCODES.BAT program that show the codes returned by GetKey.exe for all keys in keyboard, including Shift-, Ctrl- and Alt- combinations.
PS - If you are reluctant to use a third-party .exe program, just think that the original choice command is also an .exe file with a 35 KB size, but my GetKey.exe file is just 1536 bytes size. You may review several of my auxiliary .exe files and the replies posted by users of these programs at the same link.

Answer 4

Another multithread method, this time using Xcopy to capture input.
Handles all ASCII printable characters in the range 32 ~ 126, as well as TAB, Carriage Return and Backspace.
#Echo off
REM on relaunch, directs execution to the target label.
If not "%~1"=="" Goto:%1
REM initialize variables for the controller launcher
Set "QuitKey={BACKSPACE}"
Set "SignalFile=%TEMP%\%~n0_signal.dat"
REM Pipe the output of the function XCOPYCONTROLLER to Game to facilitate non blocking input.
Start /Wait /B "" "%~F0" XCOPYCONTROLLER 1>"%SignalFile%" | "%~F0" GAME <"%SignalFile%" 2> nul
REM end of controller launcher. Game has been quit.
Endlocal & Goto:Eof
:GAME
REM enable EDE environment to facilitate the use of posion characters.
REM More advanced gameloops use an infinite for /l loop to iterate through game logic
REM as it is parsed more efficiently by cmd.exe's interpreter.
REM such loops Require EDE to expand variables with their current value.
Setlocal EnableDelayedExpansion
:GAMELOOP
REM your game loop goes here.
Cls
Set /p "key="
If Defined key Title Lastkey= "!Key!". Press !Quitkey! to exit
Echo(%TIME%
If "!Key!"=="quit" EXIT
Set "key="
Goto:GAMELOOP
=======================================================
:XCOPYCONTROLLER by T3RRY
Setlocal EnableExtensions DISABLEdelayedExpansion
REM define unprintable characters
(Set LF=^
%= Do Not Modify. Linefeed Variable =%)
%= Escape =% for /f "Delims=" %%e in ('Echo Prompt $E^|cmd') Do Set "\E=%%e"
%= Tab =% for /f "delims= " %%T in ('robocopy /L . . /njh /njs' )do set "TAB=%%T"
%= Carriage Return =% for /f %%C in ('copy /Z "%~dpf0" nul') do set "CR=%%C"
%= BackSpace =% for /F "delims=#" %%B in ('"prompt #$H# &echo on &for %%b in (1) do rem"') do Set "BS=%%B"
Set "BS=%BS:~0,1%"
%= SUB =% copy nul sub.tmp /a > nul
for /F %%a in (sub.tmp) DO (
set "sub=%%a"
)
del sub.tmp
(TITLE )
<nul Set /P "=Press any Key to start"
REM Environment handling allows use of ! key
For /l %%C in () do (
Set "Key="
for /f "delims=" %%A in ('%SystemRoot%\System32\xcopy.exe /w "%~f0" "%~f0" 2^>nul') do If not Defined Key (
set "key=%%A"
Setlocal ENABLEdelayedExpansion
set "key=!KEY:~-1!"
If "!key!" == "!QuitKey!" (
<nul Set /P "=quit"
EXIT
) Else If "!Key!" == "%BS%" (
If "!QuitKey!" == "{BACKSPACE}" (
<nul Set /P "=quit"
EXIT
)
<nul Set /p "={BACKSPACE}"
) Else If "!Key!" == "!CR!" (
If "!QuitKey!" == "{ENTER}" (
<nul Set /P "=quit"
EXIT
)
<nul Set /p "={ENTER}"
) Else If "!Key!" == "!TAB!" (
If "!QuitKey!" == "{TAB}" (
<nul Set /P "=quit"
EXIT
)
<nul Set /p "={TAB}"
) Else (%= Echo without Linefeed. Allows output of = Key and Space =%
1> %~n0txt.tmp (echo(!Key!!sub!)
copy %~n0txt.tmp /a %~n0txt2.tmp /b > nul
type %~n0txt2.tmp
del %~n0txt.tmp %~n0txt2.tmp
)
Endlocal
)
)