Is there an easy way to set the @error macro to zero? - KiXtart.org

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#181384 - 2007-10-09 04:46 PM Is there an easy way to set the @error macro to zero?
RomanB RomanB Fresh Scripter Registered: 2006-10-20 Posts: 15 Loc: Bonn, Germany	Hi guys, though working with kix quite a while and searching the forum(s) intensively I didn't find an elegant way to reset the value of @error to zero. I always use a dummy command such as "cd .", which is always successful so that afterwards @error is 0. Does anybody know a better way? Thnx! Code: if @error<>0 ? $errormessage cd "." ;sets @error to 0 else ? "Success" endif
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#181386 - 2007-10-09 05:18 PM Re: Is there an easy way to set the @error macro to zero? [Re: RomanB]
Richard H. Richard H. Administrator Registered: 2000-01-24 Posts: 4946 Loc: Leatherhead, Surrey, UK	The easy way to set @ERROR to any value is: Code: $=Execute("Exit ErrorValueHere") Here is a very useful script I keep to hand to search for error codes that I might want to use in my own functions: Code: BREAK ON "Enter a string to search the error messages for:" Gets $a for $i = 0 to 9999 $=Execute("Exit "+$i) If InStr(@SERROR,$a) @ERROR " " @SERROR ? Endif next
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#181387 - 2007-10-09 05:20 PM Re: Is there an easy way to set the @error macro to zero? [Re: RomanB]
Glenn Barnas Glenn Barnas KiX Supporter Registered: 2003-01-28 Posts: 4401 Loc: New Jersey	Can't recall a situation where I needed the value reset, since most functions will set it, and I'll only test it where I need to know the last status. I do, however, save the error status, or at least an error flag if errors are non-fatal, something like: ; Set errflag to last error, but don't change previous value if ; the current error value is zero $ErrFlag = IIF(@ERROR, @ERROR, $ErrFlag) I suppose if I HAD to reset the macro, something like what you proposed would do it. Glenn _________________________ Actually I am a Rocket Scientist! $\:D$
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#181389 - 2007-10-09 05:25 PM Re: Is there an easy way to set the @error macro to zero? [Re: Glenn Barnas]
Richard H. Richard H. Administrator Registered: 2000-01-24 Posts: 4946 Loc: Leatherhead, Surrey, UK	Normally you won't ever need to reset @ERROR, but I used to get problems with some COM stuff which would set the error if there was a problem, but wouldn't reset it when the action succeeded. So if a failed action was followed by a successful one @ERROR would still be set. It's pretty rare, and I haven't come across it in quite a while.
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#181391 - 2007-10-09 05:42 PM Re: Is there an easy way to set the @error macro to zero? [Re: Richard H.]
RomanB RomanB Fresh Scripter Registered: 2006-10-20 Posts: 15 Loc: Bonn, Germany	Hi Richard and Glenn! Thanks! At first a question: doesn't Code: $RC=Execute("Exit 0") exit the script? Yes, I checked it out. So why doesn't the script exit??? Maybe I should illustrate the situation, in which I need this handling. I call a function which needs to check @error for its return value. This function is called within a while loop: Code: ;------------------- function pingable shell "cmd /c ping " + $machine + " >NUL" if @error=0 $pingable='yes' else $pingable='no' endif cd "." ;reset @error regardless of value od $pingable endfunction ;------------------- ... while @error=0 ... $rc = pingable($machine) ;something like next machine ... loop As I presumed that @error is kind of global I thought I have to reset it to zero when leaving the function. Regarding your answers must that be wrong? Regards, Roman Edited by RomanB (2007-10-09 05:49 PM) Edit Reason: wrong line in post, sorry
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#181394 - 2007-10-09 06:03 PM

Re: Is there an easy way to set the @error macro to zero? [Re: RomanB]

Witto

MM club member

Registered: 2004-09-29
Posts: 1828
Loc: Belgium

It is somewhere in the FAQ
http://www.kixtart.org/forums/ubbthreads...true#Post130059

BREAK ON
Dir("C:\NonExistingFile.Extension")
"Error = " @ERROR ?
"Reset Error" ?
ResetError()
"Error = " @ERROR ?
Get $SO

Function ResetError()
Exit 0
EndFunction

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#181396 - 2007-10-09 06:56 PM Re: Is there an easy way to set the @error macro to zero? [Re: RomanB]
Glenn Barnas Glenn Barnas KiX Supporter Registered: 2003-01-28 Posts: 4401 Loc: New Jersey	When you use the Exit command in kix - either from a function or the main script, you pass the argument back to the calling environment, so C:>kix32 test.kix (command prompt, calls Kix32.exe with arg "test.kix") $ = test('me!') (Kix32 runs script - Script calls Test() UDF) If $ID = 'me!' Exit 5 EndIf (Test() decides it doesn't like you, so does Exit 5 (access denied) and thus sets the @ERROR macro.) Logic in script checks Error macro and exits with same error (back to next line after Test() call..) If @ERROR @SERROR ? Exit @ERROR EndIf Back at the command prompt, the exit status of the script has been passed to the command interpreter, which can be viewed in the %ERRORLEVEL% variable. Echo %ERRORLEVEL% You don't need to CLEAR the error code, simply add the appropriate EXIT @ERROR line, so the error value from within the function is returned. This works for simple functions like yours, but logic can change as they get more complex. Consider: Code: Function Alive($Host) Shell '%COMSPEC% /c Ping ' + $Host + '>NUL:' If @ERROR $Alive = 0 ; return 0, not alive Exit @ERROR Else $Alive = 1 ; return 1, is alive Exit @ERROR ; EndIf EndFunction With this kind of logic, you can do things like Code: If Alive('some_computer') 'Some_Computer is alive!' ? Else 'Error ' @ERROR ' occured while pinging Some_Computer!' @CRLF '(' @SERROR ')' ? EndIF Give it a try... Glenn PS - Note that this example sorta works, and is OK for explaining the logic, but is not a valid or reliable method of ping checks! Edited by Glenn Barnas (2007-10-12 01:19 PM) _________________________ Actually I am a Rocket Scientist! $\:D$
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#181415 - 2007-10-10 09:23 AM Re: Is there an easy way to set the @error macro to zero? [Re: Glenn Barnas]
Richard H. Richard H. Administrator Registered: 2000-01-24 Posts: 4946 Loc: Leatherhead, Surrey, UK	Quote: As I presumed that @error is kind of global I thought I have to reset it to zero when leaving the function. Regarding your answers must that be wrong? Not totally wrong. @ERROR is a macro, but you can consider it to be a special type of global variable. When you use a KiXtart function, command, user defined function or some COM entities the value of @ERROR is automatically set to the exit / error value. If you don't explicitly set an exit value then the value of @ERROR is undefined so the simple rule is always set an exit value when leaving a UDF even if it doesn't seem to be relevant, and you won't have any problems. The exit value of a function is set by using "Exit n" where "n" is an integer. Exit only exits the execution sandbox that it is currently in - function, script or Executed() code - and returns to the calling element. If you want to shut down the entire KiXtart instance you would use Quit. BTW, you can get even trickier with Glenn's code: Code: Function Alive($Host) Shell '%COMSPEC% /c Ping ' + $Host + '>NUL:' $Alive=Not @ERROR Exit @ERROR EndFunction Do you see what I did there? $;\)$
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#181419 - 2007-10-10 01:01 PM Re: Is there an easy way to set the @error macro to zero? [Re: Richard H.]
Glenn Barnas Glenn Barnas KiX Supporter Registered: 2003-01-28 Posts: 4401 Loc: New Jersey	Without giving away Richard's sweet golfing trick, the point we're trying to make is that functions usually return TWO pieces of information - a Return Value and an Exit (or Status) Code. The Exit Code is zero if success, or the error code if there was an error. This is so you can tell what kind of error occurred and possibly take corrective action. The return value is the data returned by the function - the answer to the question, so to speak. That's what my function was returning - 1=alive and 0=dead. I could have returned yes/no or alive/dead values, but 1/0 are easier to process by the software. In fact, the values Zero / Not Zero are more accurate, but 1/0 are easier examples. Richard's change to my example is often used to simplify this yes/no type of logic, but won't work if you need a "real" answer, like a calculation result or name of a computer. Glenn PS - "golfing" is a term we use to reference shortening of code, thus reducing the number of (key) strokes. $;\)$ Edited by Glenn Barnas (2007-10-10 01:20 PM) Edit Reason: Added PS _________________________ Actually I am a Rocket Scientist! $\:D$
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#181460 - 2007-10-10 09:43 PM Re: Is there an easy way to set the @error macro to zero? [Re: Glenn Barnas]
RomanB RomanB Fresh Scripter Registered: 2006-10-20 Posts: 15 Loc: Bonn, Germany	Many thanks in alphabetical order $;\)$ to Glenn, Richard an Witto. Any of your approaches has its advantages depending on the situation. I really appreciate your efforts and learned a lot. My problem is the lack of colleagues doing kix, which might influence my scripting due to resulting lack of exchange of ideas. I'll try to use the forums more frequently to reduce my handicap. Regards, Roman
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#181469 - 2007-10-10 11:14 PM Re: Is there an easy way to set the @error macro to zero? [Re: RomanB]
Glenn Barnas Glenn Barnas KiX Supporter Registered: 2003-01-28 Posts: 4401 Loc: New Jersey	Groan! Already talking in Golf terms! $;\)$ Trust me - you'll get lots of idea exchange here. G- _________________________ Actually I am a Rocket Scientist! $\:D$
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#181546 - 2007-10-12 09:03 AM Re: Is there an easy way to set the @error macro to zero? [Re: Glenn Barnas]
Jochen Jochen KiX Supporter Registered: 2000-03-17 Posts: 6380 Loc: Stuttgart, Germany	Originally Posted By: Glenn Barnas Code: Function Alive($Host) Shell '%COMSPEC% /c Ping ' + $Host + '>NUL:' If @ERROR $Alive = 0 ; return 0, not alive Exit @ERROR Else $Alive = 1 ; return 1, is alive Exit @ERROR ; EndIf EndFunction PS - Note that this example sorta works, and is OK for explaining the logic, but is not the most reliable method of ping checks! Whoa Glenn, you should mention this more strongly! It is not just not the most reliable method, it's simply NO Method ! It will happily report 'Alive' state no matter what is fact on the other end of the line until you delete ping.exe or something _________________________
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#181547 - 2007-10-12 09:12 AM Re: Is there an easy way to set the @error macro to zero? [Re: Jochen]
Jochen Jochen KiX Supporter Registered: 2000-03-17 Posts: 6380 Loc: Stuttgart, Germany	I seem bound to repeat that again and again * The only way to use ping is this: Code: Function Alive($Host) shell '%COMSPEC% /c Ping ' + $Host + ' \|find /c "TTL=" >nul 2>nul' If @ERROR $Alive = 0 ; return 0, not alive Exit @ERROR Else $Alive = 1 ; return 1, is alive Exit @ERROR ; EndIf EndFunction _________________________
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#181548 - 2007-10-12 09:21 AM Re: Is there an easy way to set the @error macro to zero? [Re: Jochen]
Richard H. Richard H. Administrator Registered: 2000-01-24 Posts: 4946 Loc: Leatherhead, Surrey, UK	Quote: I seem bound to repeat that again and again Hey Guys, Jochen still hasn't realised that when we post PING code we strip out the TTL check, just to wind him up. Teehee. $\:\/$
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#181550 - 2007-10-12 10:15 AM Re: Is there an easy way to set the @error macro to zero? [Re: Jochen]
Witto Witto MM club member Registered: 2004-09-29 Posts: 1828 Loc: Belgium	Maybe you should write an UDF for this?
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#181554 - 2007-10-12 10:59 AM Re: Is there an easy way to set the @error macro to zero? [Re: Witto]
Allen Allen KiX Supporter Registered: 2003-04-19 Posts: 4563 Loc: USA	He did... it's just so old that it falls outside of the search paramaters... Ping() - http://www.kixtart.org/forums/ubbthreads...=true#Post82068
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#181555 - 2007-10-12 11:58 AM Re: Is there an easy way to set the @error macro to zero? [Re: Allen]
Witto Witto MM club member Registered: 2004-09-29 Posts: 1828 Loc: Belgium	It is slightly different. It writes p.e. a temporary file to a directory that is maybe not accessible for the user??? The above function works without any temp file. Much nicer.
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#181557 - 2007-10-12 01:24 PM Re: Is there an easy way to set the @error macro to zero? [Re: Witto]
Glenn Barnas Glenn Barnas KiX Supporter Registered: 2003-01-28 Posts: 4401 Loc: New Jersey	How did this go from discussing the proper way of returning from functions to discussing how bad our simple ping example was? $;\)$ Mebbe I should go back and highlight it in 14pt, bold, red text? (oh, wait.. I did!) $\:D$ What if I attach virtual cattle prods preventing anyone else from actually using the "shockingly bad" code? $\:o$ (dang - where's that "fried" emoticon when you need it?) $\:\)$ Glenn _________________________ Actually I am a Rocket Scientist! $\:D$
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#181575 - 2007-10-12 11:46 PM Re: Is there an easy way to set the @error macro to zero? [Re: Glenn Barnas]
RomanB RomanB Fresh Scripter Registered: 2006-10-20 Posts: 15 Loc: Bonn, Germany	$\:D$ lots of fun " ... nobody expects the spanish [scripting] inquisition. Our chief weapon is surprise, surprise and fear ... ... and ruthless efficiency ..." Apart from the fact that I didn't even dream of rising SUCH a discussion: should mention that Jochen forgot the "-n 1" parameter, which is very gut regarding golfing aspects, but performance ... just kidding! And Witto, what means p.e.? "Par exemple"? Please don't mind, je ne me moque pas de toi. Roman $;\)$ Edited by RomanB (2007-10-13 12:23 AM) Edit Reason: thinkin
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#181601 - 2007-10-14 07:21 PM Re: Is there an easy way to set the @error macro to zero? [Re: Witto]
Jochen Jochen KiX Supporter Registered: 2000-03-17 Posts: 6380 Loc: Stuttgart, Germany	Originally Posted By: Witto It is slightly different. It writes p.e. a temporary file to a directory that is maybe not accessible for the user??? The above function works without any temp file. Much nicer. It writes to a temporary file only if the caller wishes to retrieve the IP-Address from a given name, if the focus is just on returning failure or success it doesn't do it ... gawd, nobody really reads my code $;\)$ _________________________
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