how to remove trailing and leading whitespace for user-provided input in a batch file?

Question

I know how to do this when the variable is pre-defined. However, when asking for the user to enter in some kind of input, how do I trim leading and trailing whitespace? This is what I have so far:

@echo off

set /p input=:
echo. The input is %input% before

::trim left whitespace
for /f "tokens=* delims= " %%a in ("%input%") do set input=%%a
::trim right whitespace (up to 100 spaces at the end)
for /l %%a in (1,1,100) do if "!input:~-1!"==" " set input=!input:~0,-1! 

echo. The input is %input% after

pause

Thank you! :)

Answer 1

  @echo off & setlocal enableextensions
  rem enabledelayedexpansion
  set S=  This  is  a  test
  echo %S%.
  for /f "tokens=* delims= " %%a in ('echo %S%') do set S=%%a
  echo %S%.
  endlocal & goto :EOF

from http://www.netikka.net/tsneti/info/tscmd079.htm

for removing leading spaces.

Answer 2

You need to enable delayed expansion. Try this:

@echo off
setlocal enabledelayedexpansion
:blah
set /p input=:
echo."%input%"
for /f "tokens=* delims= " %%a in ("%input%") do set input=%%a
for /l %%a in (1,1,100) do if "!input:~-1!"==" " set input=!input:~0,-1!
echo."%input%"
pause
goto blah