Batch if file not exist create else rename - batch-file

Question

if not defined filename set filename=123.txt
if not defined folder set folder=January
set BASE_DIR=C:\Users\xxx\Desktop\
set file=%BASE_DIR%%folder%\%filename%
I am having difficult time coming with algorithma to accomplish what I am trying to do.
Every time this batch script runs filename and foldercan be different.
I am trying to check if file exist if it does no need to do
anything goto end.
If file does NOT exist and there is a another file under that folder. I need to update that filename with given.
However, there might be case where I wouldnt even have folder exist.
In that case I need to make folder and file inside of that folder.
Content inside file is always empty.
I dont need code, I just need help with logic to accomplish this.

Answer 1

This commented batch file should be helpful for you to finish your batch file coding task:
#echo off
setlocal EnableExtensions DisableDelayedExpansion
if not defined FileName set "FileName=123.txt"
if not defined Folder set "Folder=January"
set "BASE_DIR=%UserProfile%\Desktop"
set "FilePath=%BASE_DIR%\%Folder%"
set "FullFileName=%FilePath%\%FileName%"
rem Exit batch file execution if file already exists.
if exist "%FullFileName%" goto :EOF
rem Create the entire directory structure for the file if directory
rem does not already exist. Note the backslash at end which prevents
rem condition evaluating to true if a file with name "%Folder%"
rem exists in "%BASE_DIR%".
if not exist "%FilePath%\" md "%FilePath%" 2>nul
rem The creation of the directory tree could fail for various reasons.
if not exist "%FilePath%\" (
echo Error by %~f0:
echo/
echo Directory "%FilePath%" could not be created.
echo/
pause
goto :EOF
)
rem Add here more code to create/copy/move file "%FileName%" in/to "%FilePath%".
rem For example creating an empty file:
type NUL >"%FullFileName%"
For understanding the used commands and how they work, open a command prompt window, execute there the following commands, and read entirely all help pages displayed for each command very carefully.
echo /?
endlocal /? ... not explicitly used here. cmd.exe automatically restores previous environment on terminating batch file execution. See this answer for details about the commands SETLOCAL and ENDLOCAL.
goto /?
if /?
md /?
rem /?
set /?
setlocal /?
type /?
See also:
Where does GOTO :EOF return to?
How to create empty text file from a batch file?
Microsoft's command-line reference
SS64.com - A-Z index of the Windows CMD command line
Wikipedia article about Windows Environment Variables for environment variable UserProfile.