Remove trailing spaces from a file using Windows batch?

Question

How could I trim all trailing spaces from a text file using the Windows command prompt?

Answer 1

There is a nice trick to remove trailing spaces based on this answer of user Aacini; I modified it so that all other spaces occurring in the string are preserved. So here is the code:

@echo off
setlocal EnableDelayedExpansion

rem // This is the input string:
set "x=  This is   a text  string     containing  many   spaces.   "

rem // Ensure there is at least one trailing space; then initialise auxiliary variables:
set "y=%x% " & set "wd=" & set "sp="

rem // Now here is the algorithm:
set "y=%y: =" & (if defined wd (set "y=!y!!sp!!wd!" & set "sp= ") else (set "sp=!sp! ")) & set "wd=%"

rem // Return messages:
echo  input: "%x%"
echo output: "%y%"

endlocal

However, this approach fails when a character of the set ^, !, " occurs in the string.