Runtime.getRuntime（）。exec如何运行goto命令

Question

I'm trying to run small command-line code in java application to delete itself. So the command would keep running and keeps trying to delete the file, and once the application is closed it would be deleted.

I've tired passing the command into Runtime.getRuntime().exec but still unable to have it work.

eg:

SET file="program.jar"
goto :d
:r
timeout /t 1
:d
del %file%
if exist %file% goto :r

Tried doing this which obviously looks wrong. I've tired using ; instead of && but doesn't work either.

Runtime.getRuntime().exec("cmd /c \"SET file=\"program.jar\" && goto :d && :r && timeout /t 1 && :d && del %file% && if exist %file% goto :r\"");

Works perfectly well in a .bat file but how do i implement it into java .exec() method. I could just run the .bat file but I would want all the code be contained inside java.

Answer 1

First, you can't use labels an goto s in a cmd one-liner. Use some kind of while TRUE loop instead. In cmd terms: for /L %a in (1 0 2) do ...

Second, you need to apply Delayed Expansion . Proof:

==> SET "_file=init.ext"

==> SET "_file=prog.jar" & for /L %a in (1 1 2) do @echo %_file% %time% & timeout /T 3 1>NUL
init.ext  8:05:55,33
init.ext  8:05:55,33

==> set _file
_file=prog.jar

In above example, %_file% and %time% variables are expanded in parse time.
On the other side, with delayed expansion enabled: !_file! and !time! variables are expanded in execution time:

==> SET "_file=init.ext"

==> cmd /E /V /C SET "_file=prog.jar" ^& for /L %a in (1 1 2) do @echo !_file! !time! ^& timeout /T 3 1^>NUL
prog.jar  8:08:55,42
prog.jar  8:08:58,18

Hence, your one-liner could look as follows (verified from Windows cmd CLI for a locked file; loops until unlocked):

cmd /E /V /C SET "_file=program.jar" ^& for /L %a in (1 0 2) do if exist "!_file!" (del "!_file!" ^& timeout /T 2) else (exit /B)