:: is essentially a blank label that can never be jumped to, whereas
REM
is an actual command that just does nothing. In neither case (at least
on Windows 7) does the presence of redirection operators cause a
problem.
However,
:: is known to misbehave in blocks under
certain circumstances, being parsed not as a label but as some sort of
drive letter. I'm a little fuzzy on where exactly but that alone is
enough to make me use
REM exclusively. It's the documented and supported way to embed comments in batch files whereas
:: is merely an artifact of a particular implementation.
Here is an example where
:: produces a problem in a
FOR loop.
This example will
not work in a file called
test.bat on your desktop:
@echo off
for /F "delims=" %%A in ('type C:\Users\%username%\Desktop\test.bat') do (
::echo hello>C:\Users\%username%\Desktop\text.txt
)
pause
While this example will work as a comment correctly:
@echo off
for /F "delims=" %%A in ('type C:\Users\%username%\Desktop\test.bat') do (
REM echo hello>C:\Users\%username%\Desktop\text.txt
)
pause
The problem appears to be when trying to redirect output into a file. My best guess is that it is interpreting
:: as an escaped label called
:echo.
