Avoiding Spaghetti Code in Batch Files

I've been reading how to avoid spaghetti code in batch files(Batch files - GOTO, and How To Avoid "Spaghetti Code").

In the example of what spaghetti code is, I realized that the batch file that I use when I logon almost fits this example. Could someone please help me make my batch file more robust, and not have spaghetti code?

Code:

@ECHO OFF
CLS


:MENU
echo Welcome %USERNAME%

echo 1 - Start KeePass
echo 2 - Backup
echo 3 - FireFox
echo 4 - Exit

SET /P M=Please Enter Selection, then Press Enter:

IF %M%==1 GOTO StarKeePass
IF %M%==2 GOTO Backup
IF %M%==3 GOTO FireFox
IF %M%==4 GOTO :EOF
GOTO MENU


:StarKeePass
SET keePass="%USERPROFILE%\KeePass\KeePass-2.30\KeePass.exe"
SET kdb="%USERPROFILE%\KeePass\PasswordDatabase\PasswordDatabase.kdbx"

echo I'll start KeePass for You
START "" %keePass% %kdb% 

GOTO MENU

:Backup
SET backup="%USERPROFILE%\backup.bat"
call %backup%

GOTO MENU

:FireFox
cd "C:\Program Files (x86)\Mozilla Firefox\"
start firefox.exe

GOTO MENU

Hi JBourne,

I'm impressed with your athirst for better looking code. But you should realise that batch was never designed to be pretty; it's probably the most ugliest language there is. Be as messy as you want. Certainly, no one is ever going to tell you off for spaghetti code in batch.

That being said, I do very much dislike Goto myself. Using Goto is generally considered bad practise because it is notorious for making code an unsightly mess: "spaghetti code". I'd never use a Goto statement in a batch if I could. Unfortunately, there are a couple of instances in batch where you are pretty much forced use Goto. For instance, if you need to instate a while loop (which batch doesn't provide a statement for), there's not much choice but to construct one out of labels and Gotos.

In most cases a label and its associated Goto can be replaced by a function. Functions neaten programs by giving them more 'structure'. Though batch files don't have real functions, a nice standard has been developed. Here's an example of using functions in batch, complete with parameters and return values:

FunctionsInBatch.bat

Code:

@echo off
goto :main

:add_two_numbers Num1 Num2
setlocal
	set /a result=%1 + %2
endlocal & set /a result=%RESULT%
goto :eof

:multiply_two_numbers Num1 Num2
setlocal
	set /a result=%1 * %2
endlocal & set /a result=%RESULT%
goto :eof

:evaluate_two_numbers Num1 Num2 Operator
setlocal
	set /a result=%1 %3 %2
endlocal & set /a result=%RESULT%
goto :eof

:main
set/p=12 plus 6 is <NUL
call :add_two_numbers 12 6
echo %RESULT%!

set/p=4 times 26 is <NUL
call :multiply_two_numbers 4 24
echo %RESULT%!

set/p=the remainer of 99 divided by 4 is <NUL
call :evaluate_two_numbers 99 4 %%%%
echo %RESULT%!

If you wish to implement functions effectively in batch, I suggest studying RootOfTheNull's (channel now renamed to 'John Hammond') Basic Functions tutorial up to his tutorial #26. I highly recommend watching a hand full of that YouTuber's batch series if you wish to delve deeper into the anomalous language of batch.


JBourne, for your interest, I've rewritten your batch file the exact way I would write it.

Code:

@echo off
goto :main

:StarKeePass
	set keePass="%USERPROFILE%\KeePass\KeePass-2.30\KeePass.exe"
	set kdb="%USERPROFILE%\KeePass\PasswordDatabase\PasswordDatabase.kdbx"
	echo I'll start KeePass for You
	START "" %keePass% %kdb%
goto :eof

:Backup
	set backup="%USERPROFILE%\backup.bat"
	call %backup%
goto :eof

:FireFox
	start "" "C:\Program Files (x86)\Mozilla Firefox\firefox.exe"
goto :eof

:main
cls
echo.& echo Welcome %USERNAME%,& echo.
echo   1 - Start KeePass
echo   2 - Backup
echo   3 - FireFox
echo   4 - Exit
echo. 

choice /c "1234" /t 20 /d "4" /m "Please Type Selection, then Press Enter:"
echo.
if not errorlevel 2 call :StarKeePass
if not errorlevel 3 call :Backup
if not errorlevel 4 call :FireFox
if not errorlevel 5 goto :eof
goto :main

Note the "goto :main" near the top of the script can be found in all my batch files that use functions, which, aside from creating while loops (such as the functionality of the "goto :main" at the bottom), is the only time I would reckon to use a Goto.


If I must state a conclusion here, forget that Robvanderwoude article and just go with a style that you enjoy writing in, which is easy for you to read. A script will be better managed if you write it yourself.

Pyro has it right. Cmd batch language is lame. It traces its roots back to the early '70s with the CP/M operating system. It was garbage in the 20th century, and ought to be abolished in the 21st.

If you want better code, use a better language.
bash is better.
powershell is better.

Ztruker said:

You have 4 Gotos in your batch file, JBourne also had 4 :) :)

Just sayin ...

Well, as you know, "goto :eof" takes on a special meaning. Most of the "goto :eof" statements in my batch program, specifically the ones that conclude each function, may of course be replaced with "exit /b" which is functionally equivalent to "goto :eof". "Goto :eof" is just more commonly used by batch-ers than "exit /b" for some reason.

Furthermore, rearranging the structure of the program slightly, moving the ":main" section further to the top of the script will eliminate another Goto. But this would mean having functions below the main algorithm. It is good programming practise to declare functions and variables at the top of a program.

Here's the batch file I describe, which has as few Gotos as possible.

Code:

@echo off
:main
cls
echo.& echo Welcome %USERNAME%,& echo.
echo   1 - Start KeePass
echo   2 - Backup
echo   3 - FireFox
echo   4 - Exit
echo. 
 
choice /c "1234" /t 20 /d "4" /m "Please Type Selection, then Press Enter:"
echo.
if not errorlevel 2 call :StarKeePass
if not errorlevel 3 call :Backup
if not errorlevel 4 call :FireFox
if not errorlevel 5 exit /b
goto :main
 
:StarKeePass
	set keePass="%USERPROFILE%\KeePass\KeePass-2.30\KeePass.exe"
	set kdb="%USERPROFILE%\KeePass\PasswordDatabase\PasswordDatabase.kdbx"
	echo I'll start KeePass for You
	start "" %keePass% %kdb%
exit /b
 
:Backup
	set backup="%USERPROFILE%\backup.bat"
	call %backup%
exit /b
 
:FireFox
	start "" "C:\Program Files (x86)\Mozilla Firefox\firefox.exe"
exit /b

... The result is a grand total of one Goto statement. This last Goto cannot be avoided as it is part of a while loop construct—using Gotos and labels is the only stable way to replicate a while loop in the batch language.

margrave said:

Cmd batch language is lame. [...] It was garbage in the 20th century, and ought to be abolished in the 21st.

Unfortunately or fortunately, we won't be seeing batch files completely disappear from our Windows any time soon—only fade.

Here's what PowerShell expert Jeffrey Snover (one of the designers and developers of PowerShell) had to say about batch files when they were mentioned in an interview about PowerShell,

Erik Meijer: And so no more batch files now--?
Jeffrey Snover: Well, they'll still be there. They're like some... disease you die with but not of. Uh, and...
Erik Meijer & Jeffrey Snover: *chuckles*
Jeffrey Snover: Well, you know, you can't get rid of that stuff. But yeah, I think you'll see fewer and fewer usages of them.

Ztruker said:

Batch is the easiest for novices though.

Though that is up for debate. I'm sure many would agree that PowerShell is more intuitive and user-friendly than batch.

The more sophisticated programmers avoid "goto" statements[1] by using the "comefrom"[2]:

1: E. W. Dijkstra, "GOTO Statement Considered Harmful," Letter of the Editor, Communications of the ACM, March 1968
2: Clarke, Lawrence, "We don't know where to GOTO if we don't know where we've COME FROM. This linguistic innovation lives up to all expectations.", Datamation, 1973