Exiting a batch file without exiting the command shell -and- batch file subroutines

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

skSdnW — Fri, 03 Aug 2012 15:34:41 GMT

@Kenn:

This forces you to know when you are executing a batchfile, not really nice when you have a batch implementation of which etc

[You can play it safe and put call in front of everything. -Raymond]

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

Kenn — Fri, 03 Aug 2012 10:23:43 GMT

@WndSys

You can work around this by always using CALL to run a batch file.

Let's say script.bat exits with EXIT /B 0 on success and EXIT /B 1 on error. The following is not reliable when run from an interactive command prompt:

script.bat && echo OK

script.bat || echo failed

However, this works:

call script.bat && echo OK

call script.bat || echo failed

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

DavidPLB — Fri, 03 Aug 2012 01:11:08 GMT

(This algorithm erroneously reports that no files require one disk. Fixing that is left as an exercise.)

change

set DISKSIZE=1474560

set CLUSTER=512

set DISKS=1

set TOTAL=0

set DISKSIZE=1474560

set CLUSTER=512

set DISKS=0

set TOTAL=%DISKSIZE%

so set the imaginary 0 disk to be full such that teh firt fil will alwasy 'not fit' and overflow to first disk.

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

Joshua — Thu, 02 Aug 2012 21:21:43 GMT

@Skyborne: I can reduce away this Knapsack problem easily if it were worth my while.

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

voo — Thu, 02 Aug 2012 20:55:20 GMT

@Skyborne Think so too. So clearly the next step is dynamic programming with batch files!

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

Skyborne — Thu, 02 Aug 2012 19:42:38 GMT

@pinwing, I think we're looking at an instance of the Knapsack Problem, in which case finding the optimal packing knowing everything beforehand is NP-complete... and the batch file only looks at items streaming past one loop at a time.

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

pinwing — Thu, 02 Aug 2012 17:11:14 GMT

Hmm, the number of floppies seem to be at least 2.

I guess DISK should be initialized to 1?

Also, if I have files a.txt (1 byte), b.txt (1474560-512 bytes) and c.txt (1 byte), then it may come to the conclusion that all files need on their own floppy (instead of putting a.txt and c.txt together).

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

skSdnW — Thu, 02 Aug 2012 17:04:51 GMT

A big problem with exiting batch files is that they don't set the exit/error code used by cmd.exe for && and || handling:

test.cmd:

@echo off

call Fail\This\Line.exe

if errorlevel 1 (echo.ErrorMessageHere&exit /b 1)

echo Should not get here

Then in cmd.exe run: test&&echo.OK||echo.Failed

To fix it you can use ugly workarounds:

@echo off

call Fail\This\Line.exe

if errorlevel 1 (echo.ErrorMessageHere&goto dieerrlvl)

echo Should not get here

:dieerrlvl

%comspec% /c exit %errorlevel%

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

Stefan Kanthak — Thu, 02 Aug 2012 16:52:00 GMT

EXIT and EXIT /B have another advantage over GOTO :EOF

they can return an errorlevel.

BUT: dont try to use IF ERRORLEVEL with negative values

--- ERRORLEVEL.CMD ---

%SystemRoot%\System32\Cmd.Exe /C Exit -1

Echo ERRORLEVEL: %ERRORLEVEL%

If ERRORLEVEL 0 (Echo OK [0 ^> -1]) Else (Echo ERROR [0 ^<= -1])

--- eof ---

@Raymond: it doesnt hurt to write always GOTO :label

re: Exiting a batch file without exiting the command shell -and- batch file subroutines

Programmerman — Thu, 02 Aug 2012 16:20:18 GMT

It does feel like the single greatest skill a batch file writer can have is complete knowledge of the FOR command and all the ways it can be abused.