Determine filename length from a batch file - batch-file

Question

I need to work two things into a .bat file I am working on for a little project. First things first, I have to know if any filename contained into the same folder (recursively) I launch my .bat in is any longer than 100 characters. If so, I need to make it 92 characters long and keep the extensions.
For example, I have this filename:
IncrediblyLongFileNameIAmSorryForThisItLooksLikeSomeDamnSpamJesusIAintEvenCloseTo100yetalmostwaitforitYEAH.omg
The above filename is 110 characters. I need to keep the extension, therefore the program should rename the file as this:
IncrediblyLongFileNameIAmSorryForThisItLooksLikeSomeDamnSpamJesusIAintEvenCloseTo100yetalmos.omg
So far, my main problem is that I don't know how to work with filename strings in batch. I used this code:
#echo off & setlocal enableextensions
FOR /R %%i IN (*.*) DO (
ECHO %%~nxi
FOR /f "delims=:" %%a in ('
^(echo."%%~nxi"^& echo.^)^|findstr /o .'
) DO set lenght=%%a-5
echo The length of "%%~nxi" is %lenght%
)
endlocal & goto :EOF
But I can't SET inside a FOR, and it can't do basic math either (i.e. it can't do the -5 operation).
The second thing, which I believe should be easier once the first one is done, is simply to compare all the filenames in the folder (recursive, once again) and make sure no filenames are the same. If the program finds any filenames that are the same, the second occurrence should be renamed to add something like l1l at the end. (I can't use parentheses here, therefore I use two ls instead to cover the number.) The only thing you need to take care of is the file extensions, because I can't add anything after the file extensions, lest they become unusable.
Can anyone offer explanations for how to accomplish this? I would really like to be able to work this out myself, but I simply lack experience in batch programming.

Answer 1

#ECHO OFF
SETLOCAL
SET "sourcedir=c:\sourcedir"
SET "tempfile=%temp%\##fn##.92"
ECHO ::>"%tempfile%"
FOR /f "delims=" %%a IN (
'dir /s /b /a-d "%sourcedir%\*" '
) DO (
SET "fullname=%%a"
SET "name=%%~na"
SET "ext=%%~xa"
CALL :chgname
)
del "%tempfile%"
GOTO :EOF
:chgname
:: Proposed new name part - first 92 characters of existing name
:: also prepare for adding modifier
SET "newname=%name:~0,92%"
SET /a modifier=0
:modl
:: See whether this name has already been found
ECHO %newname%%ext%|FINDSTR /b /e /i /g:"%tempfile%" >NUL
IF ERRORLEVEL 1 GOTO makechange
:: existing name - modify it
SET "newname=%name:~0,92%#%modifier%#"
SET /a modifier+=1
GOTO modl
:makechange
IF "%name%" NEQ "%newname%" ECHO REN "%fullname%" "%newname%%ext%"
>>"%tempfile%" ECHO %newname%%ext%
GOTO :eof
Reasonably simple problem.
Get a directory-list in basic form (full-filename only) and apply the full filename, name part and extension part to appropriately-named variables.
Manipulate the filename to a new name consisting of the first 92 characters of the original name part. Anticipate the need to modify this new name by establishing a modifier to optionally be applied.
See whether the proposed new name already exists in the temporary file of NEW names already processed. If not found on that file, safe to rename (if required) and record name used.
If the filename has already been used, modify it to the original first 92+ "#anumber#", increment the modifier in anticipation and try again.
Only two comments required further - first, I used # rather than ! because ! has a special meaning to batch. Second, writing :: to the tempfile (the name of the tempfile is irrelevant - I chose one that's unlikely to exist...) means that findstr doesn't complain because the file is empty, but :: can't possibly be a real filename.
The /b /e /i options to findstr mean that the name echoed in must exactly match a line (matches both /b - begin and /e - end) but /i - case is irrelevant.