Batch FOR /F loop won't read relative directory - loops

Question

I have a simply FOR /F loop which strips out all but one line of a text file:
for /f "skip=12 tokens=* delims= " %%f in (.\NonProcessed\*.txt) do (
> newfile.txt echo.%%f
goto :eof
)
But when I run, I get the result:
The system cannot find the file .\NonProcessed\*.txt
The for loop works fine if I enter a fully qualified path to the text file within the brackets, but it can't handle the relative link I have in there. I've been able to use the exact same relative link in another standard for loop in a different batch file running in the same directory without any issues. I can't understand why it won't work! Please help.
EDIT: For comments, code I'm using now is
for %%f in (.\NonProcessed\*.txt) do (
echo f is %%f
for /f "usebackq skip=12 tokens=* delims= " %%a in (%%f) do (
echo a is %%a
> %%f echo.%%a
goto :continue
)
:continue
sqlcmd stuff here
)

Answer 1

Sorry but for /f does not allow you to do that. And no, the problem is not the relative path to files but the wildcard.
According to documentation, you have the syntax case
for /F ["ParsingKeywords"] {%% | %}variable in (filenameset) do command [CommandLineOptions]
For this case, documentation states The Set argument specifies one or more file names. You can do
for /f %%a in (file1.txt file2.txt file3.txt) do ...
but wildcards are not allowed.
If you don't know the name of the file you want to process, your best option is to add an additional for command to first select the file
for %%a in (".\NonProcessed\*.txt"
) do for /f "usebackq skip=12 tokens=* delims= " %%f in ("%%~fa"
) do (
> newfile.txt echo(%%f
goto :eof
)
When executed, the goto command will cancel both for loops so you end with the same behaviour you expected from your original code.
edited to adapt code to comments
#echo off
set "folder=.\NonProcessed"
pushd "%folder%"
for /f "tokens=1,2,* delims=:" %%a in (
' findstr /n "^" *.txt ^| findstr /r /b /c:"[^:]*:13:" '
) do (
echo Overwrite file "%%a" with content "%%c"
>"%%a" echo(%%c
)
popd
Read all the files in the folder, numbering the lines. The output for the first findstr command will be
filename.txt:99:lineContents
This output is parsed to find the line 13, the resulting data is splitted using the colon as a separator, so we will end with the file name in %%a, the line number in %%b and the line content in %%c.

Answer 2

SET FILES_LIST=files_list.config
DIR /b .\NonProcessed\*.txt>!FILES_LIST!
for /f "skip=12 tokens=* delims= " %%f in (!FILES_LIST!) do (
> newfile.txt echo.%%f
goto :eof
)
IF EXIST "!FILES_LIST!" DEL "!FILES_LIST!"
I did not check how your's FOR works, just added my additions/corrections to it.... Hope it will work for you.
Best regards!