仅一行cmd：替换文件名不起作用？

Question

I'm trying to replace an file name but it doesnt work.

I know that this works: (command line, no .bat file!)

SET G="test string"
echo %G:s=a%

But if i use a for loop it doesnt work. Why? (command line, no .bat file!)

for /r . %G in (*.jpg) do echo %G:s=a%

Thanks for help in Advance!

Answer 1

A for loop in a BAT needs to double the "%%". Also, the for variable doesn't support substitutions, and variables get substituted before executed.

For /r . %%G in (*.jpg) do @echo %%G

Try this:

setlocal ENABLEDELAYEDEXPANSION
for %%g in (*.JPG) do @set Q=%%g && echo !Q:t=X!

Answer 2

You are confusing a Batch variable with a FOR command replaceable parameter . In these lines:

SET G="test string"
echo %G:s=a%

The G is a Batch variable, but in this one:

for /r . %G in (*.jpg) do echo %G:s=a%

The G is a FOR replaceable parameter and the substring replacement only works on Batch variables. The solution is to assign the FOR parameter into a Batch variable and then do the replacement. However, the only way to do so is via delayed expansion , so the solution is this:

cmd /V:ON /C for /r . %G in (*.jpg) do @set "G=%G" ^& echo !G:s=a!

For further details, search this site for "delayed expansion" or type cmd /? and set /? , and carefully read "delayed expansion" references.