:GetIN [ReturnVar] ["qouted findstr search pattern"]  [Optional:"/C" - required for patterns with spaces]
@Echo off
 SETLOCAL EnableExtensions EnableDelayedExpansion
rem - lines prefixed with ::: form part of this scripts Help Documentation. Do not remove.
> "%TEMP%\%~n0_help.~tmp" (For /F "Delims=" %%G in ('Type "%~f0"^| Findstr.exe /BLIC:":::" 2^> nul ')Do For /F "Tokens=1* Delims=:" %%v in ("%%G")Do Echo/^|%%v)
:::================================================================================================================
:::     [ GetIn Input function or standalone script for validating input with findstr regular expressions. ]
:::                     Version = 2.2        Release = October 2020       Author = T3RRY 
:::========================================= ^^^! important notes on usage ^^^! =========================================
:::          ^^^! Pipes not supported ^^^!
:::    ^     + Not suited for use with pipes due to forced loop for failed matches
:::  < ^^^! >   + Test your regex pattern to ensure it is valid for the required input
:::    v       format to prevent your user/s being stuck in a goto loop.
:::            Error output for invalid search patterns is not displayed.
:::          + EXIT.CODES - Errorlevel assessment after call:
:::            - Errorlevel 3 - User has failed to provide input * OR * regex pattern is
:::              invalid * OR * GetIn is a called label in a file that has recieved input
:::              from a pipe that has not been handeled before the call.
:::            - Errorlevel 2 - GetIn is a script that has been invoked by a pipe
:::            - Errorlevel 1 - GetIn help has been Invoked * OR * GetIn has been called
:::              without Arg 2 for Regex Pattern
:::            - Errorlevel 0 - Input has been assigned that matches the regex Pattern
:::================================================================================================================
rem [* Display GetIn Usage with findstr regex info and practical examples *]
>> "%TEMP%\%~n0_help.~tmp" (
  Echo/^| USAGE: Call %~0 [ReturnVar] ["findstr search pattern"] [Optional:"/C" -required for patterns with spaces]
  Echo/^|================================================================================================================
  Echo/^| Examples [ Description is replaced with Arg 1-ReturnVar ]:
  Echo/^|
  Echo/^|    Call %~0 4-Digit-Number "[0-9][0-9][0-9][0-9]"
  Echo/^|    Call %~0 Alphanumeric-String "[0-9a-zA-Z]*"
  Echo/^|    Call %~0 semicolon-delimited-hexadecimal-String "[0-9a-fA-F][0-9a-fA-F][:][0-9a-fA-F][0-9a-fA-F]"
  Echo/^|    Call %~0 AlphaString-with-3-Digit-Numeric-suffix "[a-zA-Z]*[0-9][0-9][0-9]"
  Echo/^|    Call %~0 list-of-delimited-words "[a-zA-Z, ]*" /C
  Echo/^|    Call %~0 pair-of-delimited-numbers "[0-9]*[, ][0-9]*" /C
  Echo/^|
  Echo/^|    ^^     Limit of 15 character class expressions applies
  Echo/^|  ^< ^^^! ^>   Case sensitive classes should use actual letters as [STRING] instead of range [A-Z]
  Echo/^|    v     See: https://stackoverflow.com/a/20159191/12343998
  Echo/^|                                                     -Note: %~0 does not support Input from pipes.
  Echo/^|----------------------------------------------------------------------------------------------------------------
  For /F "Delims=" %%G in (' Findstr.exe /? ^| More +33 ') Do Echo/^|  %%G
  Echo/^|  https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/findstr
  Echo/^|  recommended reference: https://stackoverflow.com/questions/8844868/
   Echo/\================================================================================================================
 )
(Set LF=^

%= Linefeed. do not modify. =%)
Set "Exit.Code=0"
rem [ test if standalone script - if so test if accessed by pipe; reject execution if true ]
 If "%~0" == "%~n0" For %%G in (!cmdcmdline!)Do Echo/%%~G|Findstr.exe /LIC:"/S" > nul 2> nul && (Set "Exit.Code=2" & Goto :Usage)
:retry
 Del /Q "%TEMP%\%~n0_validate.~tmp" 2> nul
 If !Exit.Code! GTR 5 Goto :Usage
 Set "rVar=" & Set "_C=0" & Set "_S=0"
 If "%~2" == "" GOTO :Usage
 Setlocal DISABLEdelayedExpansion & rem ::: dispay occurances of carets [^] in pattern
 Endlocal & Set "Pattern=%~2"
  Set /P "rVar=Input Format for %1:!LF!!Pattern!!LF!!LF!Enter %1: "
 > "%TEMP%\%~n0_validate.~tmp" (Echo/!rVar!)
 If /I "%~3" == "/C" (
  TYPE "%TEMP%\%~n0_validate.~tmp"| findstr.exe /RXC:"%~2" > nul || (Set /A "Exit.Code+=1" & <nul Set /P"= ^! Invalid value.!LF!" & Goto :Retry)
 ) Else (
  TYPE "%TEMP%\%~n0_validate.~tmp"| findstr.exe /RX "^%~2$" >nul || (Set /A "Exit.Code+=1" & <nul Set /P"=- ^! Invalid value.!LF!" & Goto :Retry)
 )
 Echo/%1: [!rVar!] Accepted
 ENDLOCAL & Set "%~1=%rVar%"
 Del /Q "%TEMP%\%~n0_validate.~tmp"
 Exit /B 0
:Usage
 If "%Exit.Code%" == "0" (Set "Exit.Code=1")
 If "%Exit.Code%" == "2" (
  >> "%TEMP%\%~n0_help.~tmp" (
    Echo/-------------------------------              ^^! pipes not supported ^^!              -------------------------------
    Echo/=================================================================================================================
 ))
If %Exit.Code% GTR 5 (
  >> "%TEMP%\%~n0_help.~tmp" (
   Echo/-------------------------------      ^^! Attempt limit exceeded. Input rejected ^^!   -------------------------------
   Echo/-------------------------------              ^^! pipes not supported ^^!              -------------------------------
   Echo/=================================================================================================================
  )
  Set "Exit.Code=3"
 )
 Type "%TEMP%\%~n0_help.~tmp" | ( More )
 Del /Q "%TEMP%\%~n0_help.~tmp" 2> nul
ENDLOCAL & exit /B %Exit.Code%
rem ::: [ ------------------------------------------------------------------------------------------------- End GetIn ]