Do batch files support exit traps?

Question

Do Windows .bat scripts have an exit-trap like feature, that would allow registration of cleanup actions that always need to be run?

I am not interested in any solution that uses Powershell or other shells (I already have Python installed on the target system so if that can't be done in batch files I'll just wrap a bunch of calls to subprocess.Popen in try...finally).

I want to make sure some temporary lock files get cleared at the end of the batch file. — antony, Mar 05 '15 at 23:52

score 12 · Accepted Answer · edited May 23 '17 at 12:32

No, there are no exceptions, and no formal way of registering an exit routine to run automatically upon termination.

However, you can get close if you do not need environment changes to persist after the script terminates. You can run the majority of your script in a new CMD session, and then you can have cleanup routines in the parent level that will always run upon termination as long as the console window is not killed. Control will be returned back to the outer shell if the inner script terminates normally, or terminates due to Ctrl-C, or terminates due to fatal syntax error, etc.

Here is a trivial demonstration:

@echo off
if "%~1" equ ":main" (
  shift /1
  goto main
)
cmd /d /c "%~f0" :main %*
echo Cleanup actions go here
exit /b

:main
echo Main actions go here
exit /b

UPDATE - Hacked exceptions

I have since developed an effective exception hack using nothing but native batch commands - See Does Windows batch support exception handling?.

Exceptions can be thrown at any level of your code, and the exception bubbles up until a catch block handles the exception. The code cannot recognize errors on its own - each exception must be explicitly thrown by your code. It also cannot respond to , fatal syntax errors, or closed console. But if those limitations are acceptable, then it is an extremely effective way of installing cleanup code.

EDIT - Use /D option to prevent AutoRun commands from running upon instantiation of child shell. — dbenham, Mar 06 '15 at 01:46
I thought that was what setting exit codes were for, to allow secondary batch files to execute depending on the primary batch file(s) exit code. — user4317867, Mar 06 '15 at 08:02
@user4317867 - The exit code (errorlevel) only informs the CALLer what the returned status is - it does not allow the parent to execute. If a CALLed script or label terminates abnormally due to Ctrl-C or fatal syntax error, then all batch processing terminates immediately, and control is never returned back to the CALLer. My answer uses CMD /C to address that problem. — dbenham, Mar 06 '15 at 12:04
I got "Terminate batch job ? (Y/N)" question twice when i press ctrl+c during execution of the child shell. It is annoying because this question should only appear 1 time for child shell, but not for parent immediately after... do you have any fix ? — Gosfly, Jun 16 '20 at 08:35

score 1 · Answer 2 · answered Mar 06 '15 at 00:50

Batch doesn't support anything like this.

However, cmd also doesn't have exceptions and very few ways of abnormally terminating a script (a syntax error in your script, or crashing cmd.exe for example). If your script doesn't intentionally terminate itself, it should be safe to simply put any cleanup at the end of your script.

To go further, you can call your batch file in a subshell from another batch file, and have the outer script do your cleanup. Then, no matter what happens in the script, the outer shell will just run the next command in the outer batch when it finishes.

alas what I want is to do something when the user closes the command window :| — peterk, Oct 29 '18 at 18:57

Do batch files support exit traps?

2 Answers2