Rename or remove prefix for multiple files to each ones' number in Windows

Question

I am trying to change all the files names in a current folder and I am trying to achieve this either by removing the files prefix (every file has a common prefix) or changing th

Answer 1

I don't understand why you can't use a batch file. But here is a solution that should work with most file names.

Critical - first you must make sure you have an undefined variable name, I'll use fname

set "fname="

Next is the command to actually do the renaming. It won't work properly if fname is already defined.

for %a in (prefix*.txt) do @(set "fname=%a" & call ren "%fname%" "%fname:*prefix=%")

The fname variable is defined for each iteration and then the syntax %fname:*prefix=% replaces the first occurrence of "prefix" with nothing. The tricky thing is Windows first attempts to expand %fname% when the command is first parsed. Of course that won't work because it hasn't been defined yet. On the command line the percents are preserved if the variable is not found. The CALL causes an extra expansion phase that occurs after the variable has been set, so the expansion works.

If fname is defined prior to running the command, then it will simply try to rename that same file for each iteration instead of the value that is being assigned within the loop.

If you want to run the command again with a different prefix, you will have to first clear the definition again.

EDIT - Here is a batch file named "RemovePrefix.bat" that does the job

::RemovePrefix.bat  prefix  fileMask
@echo off
setlocal
for %%A in ("%~1%~2") do (
  set "fname=%%~A"
  call ren "%%fname%%" "%%fname:*%~1=%%"
)

Suppose you had files named like "prefixName.txt", then you would use the script by executing

RemovePrefix  "prefix"  "*.txt"

The batch file will rename files in your current directory. The batch file will also have to be in your current directory unless the batch file exists in a directory that is in your PATH variable. Or you can specify the full path to the batch file when you call it.

The rules for expansion are different in a batch file. FOR variables must be referenced as %%A instead of %A, and %%fname%% is not expanded initially, instead the double percents are converted into single percents and then %fname% is expanded after the CALL. It doesn't matter if fname is already defined with the batch file. The SETLOCAL makes the definition of fname temporary (local) to the batch file.