Mass rename of file extensions recursively (windows batch)

Question

I have numerous files in a very complex directory structure, and for reasons not worth discussing I need to rename all files with the extension of \".inp\" to have \".TXT\" exte

Answer 1

for /r startdir %%i in (*.inp) do ECHO ren "%%i" "%%~ni.txt"

should work for you. Replace startdir with your starting directoryname and when you've checked this works to your satisfaction, remove the echo before the ren to actually do the rename.

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For the downvoters: executing a batch file differs from excuting from the command prompt in that each %%x where x is the metavariable (loop-control variable) needs to be reduced to %, so

for /r startdir %i in (*.inp) do ECHO ren "%i" "%~ni.txt"

should work if you execute this from the prompt. Please read the note about echo.