20080225

Batch-fu

I don't know how many avid windows batchers are out there ( I was one some years ago ), but perhaps a few of you can use / be horrified by this little helper. Ever get annoyed because you can't easily reuse functions between scripts since they'll stomp all over each others environment variables? Probably not. Just in case, here's how to create lexically scoped batch file functions.

::#
:ServerName_Service
setlocal

:: blah blah do anything to namespace blah

::now pass the full name / status back out of the setlocal
for /F "usebackq tokens=1,2 delims=~" %%a in (`echo.%ServiceName%~"%Status%"`) do (
endlocal
set CACHE~%%a=%%b
)
goto :eof

Tada!

Even better if you structure them such that the first argument is the name of the variable to receive the value from the function call and then write your exit similar to this :

::now pass the full name / status back out of the setlocal
for /F "usebackq tokens=1,2 delims=~" %%a in (`echo.%ServiceName%~"%Status%"`) do (
endlocal
set %1=%%b
)

BTW, I don't really recommend writing large programs in batch, but if draconian network policies make it all you've got, good luck.

Remember that it is two phase, first variable expansion happens, then execution occurs. Execution of lines starting with `:' makes these lines into labels. Lines that start `::' are label errors and dropped ( making for better comments than rem, which executes and freaks out all to hell if special characters are in its argument list / comment area ). Lines starting `%%en_var%%' where the environment variable `en_var' has the value `::' are label errors and dropped. ( This can be used to great effect. I can't take credit for this hack though. I found it on Rob van der Woude's scripting site ).

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(2) the subculture of the compulsive programmer, whose ethics prescribe that one silly idea and a month of frantic coding should suffice to make him a life-long millionaire. --ewd1036