Windows bat file equivelent of bash string manipulation - windows

Question

How would I achieve this:
for i in *.e; do mv $i ${i%-b*.e}.e; done
in a Windows batch file? (It renames files containing "-b" to the part before "-b". Note that this is not necessarily the end of the string! e.g. "file-b-4.e" will become "file.e")

Answer 1

If you really want to do this in batch, this should work
#echo off
setlocal disableDelayedExpansion
for %%F in (*.e) do (
set "var=%%~F"
setlocal enableDelayedExpansion
set "var=!var:-b=.e:!"
for /f "eol=: delims=:" %%A in ("!var!") do (
endlocal
echo ren "%%F" "%%A"
)
)
Edit
The comment by panda-34 alluded to the fact that the original posted code failed if the file name begins with -b. The code above was fixed by incorporating the extension into the replacement string. (thanks panda-34 for alerting me to the problem)
panda-34 also provided an alternate solution that uses command injection with search and replace. The injected command is the REM statement.
The panda-34 solution works as long as the file name does not contain & or ^ characters, but fails if it does.
Below is a modified version of the command injection technique that should work with all valid Windows file names. There are 2 critical mods, 1) make sure the special chars in the file name are always quoted, and 2) do not pass the value as a CALL argument, otherwise ^ will be doubled to ^^.
#echo off
setlocal disableDelayedExpansion
for %%i in (*-b*.e) do (
set old="%%~ni"
call :ren_b
)
exit /b
:ren_b
set v=%old:-b=.e"&rem "%
echo ren "%old:~1,-1%.e" %v%
exit /b
Final Edit (I hope):
As baruch indicates in his comment, the solutions above remove starting with the 1st occurance, whereas the original bash command removes starting with the last occurance.
Below is a version that should be an exact equivalent of the original bash command.
#echo off
setlocal disableDelayedExpansion
set "search=-b"
for %%A in (*%search%*.e) do (
set "old=%%A"
setlocal enableDelayedExpansion
set "new=\_!old:%search%=\_!"
for %%B in ("!new!") do (
endlocal
set "new=%%~pB"
setlocal enableDelayedExpansion
set "new=!new:~2,-1!.e"
echo ren "!old!" "!new:\_=%search%!"
endlocal
)
)

Answer 2

Simple, really
for %%i in (*-b*.e) do call :ren_b %%~ni
goto :eof
:ren_b
set v=%*
set v="%v:-b=.e" ^& rem %
ren "%*.e" %v%
Here's a variant to keep the name till the last -b occurence
setlocal enabledelayedexpansion
for %%i in (*-b*.e) do (
set v=%%~ni
set v=!v:-b=\!
for %%j in ("\!v!") do (
set v=%%~pj
set v=!v:~1,-1!
set v=!v:\=-b!
ren "%%i" "!v!.e"
)
)
It will fail for names containing ! and starting with -b.
P.S, Didn't see, dbenham already provided the equivalent solution, probably with more provisions for terminal cases of file names.

Answer 3

Forget it, some convenient things cannot be done in NT scripting. What you are asking here is not possible to my knowledge. And I've written and maintained complex NT scripts bigger than 50 KiB, using all kinds of tricks. The book "Windows NT Shell Scripting" points out many of these, for the same and more see Rob van der Woude's scripting pages.
I reckon you could do part of this, but certainly not in a one-liner due to how variable expansion works in NT scripting. For example you could extract the part of the string that you expect to be -b and check whether it is -b, then extract the other parts and rename from the original name to the one that is comprised of only the extracted parts.
But you'll likely need ten to fifteen lines to achieve that. In that light, consider using a different scripting language for the purpose. Especially if this is a modern Windows version.
I realize this is not the desired answer (i.e. that this is possible and a sample), but cmd.exe is very limited compared to Bash, albeit by far not as limited as some opponents of traditional batch scripting are pointing out.