How To Do Error Handling In Vbscript
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Error Handling In Vbscript Tutorial
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Vbscript Error Handling Line Number
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On Error Resume Next Vbscript W3schools
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LippertAugust 19, 200419 0 0 0 OK, enough about the Peloponnesian war -- a number of readers have asked me questions about error handling in VBScript recently, so I think I'll talk about it a bit for the next few days. Today, I vbscript goto want to very carefully describe what the error handling semantics are in the language,
Vbscript Error Message
because there is some confusion over how exactly it works. There are two statements that affect error handling in VBScript: On Error if err.number 0 then Resume NextOn Error Goto 0 The meaning of the first seems clear -- if you get an error, ignore it and resume execution on the next statement. But as we'll see, there are some subtleties. But https://technet.microsoft.com/en-us/library/ee692852.aspx before that, what the heck is up with the second statement? The second statement turns off ‘resume next' mode if it is on. Yes, the syntax is ridiculous -- something like On Error Raise would be a whole lot more clear. But for historical purposes, this is what we're stuck with. Visual Basic has an error handling mode which VBScript does not -- VB can branch to a labeled or numbered statement. (Remember https://blogs.msdn.microsoft.com/ericlippert/2004/08/19/error-handling-in-vbscript-part-one/ line numbers? Those were the days!) To tell VB that you no longer wish to branch to that statement, you give zero, an invalid line number. C'est super-beaucoup-de-fromage, n'est-ce pas? But we're stuck with it now. The subtlety in the "resume next" mode is best illustrated with an example. Const InvalidCall = 5Print "Global code start"Blah1Print "Global code end"Sub Blah1() On Error Resume Next Print "Blah1 Start" Blah2 Print "Blah1 End"End SubSub Blah2() Print "Blah2 Start" Err.Raise InvalidCall Print "Blah2 End"End Sub This prints out Global code startBlah1 StartBlah2 StartBlah1 EndGlobal code end Hold on a minute -- when the error happened, Blah1 had already turned ‘resume next' mode on. The next statement after the error raise is Print "Blah2 End" but that statement never got executed. What's going on? What's going on is that the error mode is on a per-procedure basis, not a global basis. (If it were on a global basis, all kinds of bad things could happen -- think about how you'd have to design a program to have consistent error handling in a world where that setting is global, and you'll see why it's per-procedure.) In this case, Blah2 gets an error. Blah2 is not in ‘resume next' mode, so it aborts itself, records that there was an error s
VBScript in a Nutshell by Matt Childs... Published by O'Reilly Media, Inc. VBScript in a Nutshell Preface Why This Book? Who Should Read https://www.safaribooksonline.com/library/view/vbscript-in-a/1565927206/ch04s02.html This Book? How This Book Should Be Used How This Book Is Structured Conventions in This Book How To Contact Us I. The Basics 1. Introduction 2. Program Structure 3. Data http://www.herongyang.com/VBScript/Error-Handling-On-Error-Resume-Next.html Types and Variables 4. Error Handling and Debugging 5. VBScript with Active Server Pages 6. Programming Outlook Forms 7. Windows Script Host 8. VBScript with Internet Explorer II. Reference 9. The error handling Language Reference III. Appendixes A. Language Elements by Category B. VBScript Constants C. Operators Index Colophon Error Handling Error handling does not involve finding errors in your scripts. Instead, use error handling techniques to allow your program to continue executing even though a potentially fatal error has occurred. Ordinarily, all runtime errors that are generated by the VBScript engine are fatal, since error handling in execution of the current script is halted when the error occurs. Error handling allows you to inform the user of the problem and either halt execution of the program or, if it is prudent, continue executing the program.The On Error Resume Next StatementThere are two main elements to error handling in VBScript. The first is the On Error statement, which informs the VBScript engine of your intention to handle errors yourself, rather than to allow the VBScript engine to display a typically uninformative error message and halt the program. This is done by inserting a statement like the following at the start of a procedure:On Error Resume NextThis tells the VBScript engine that, should an error occur, you want it to continue executing the program starting with the line of code which directly follows the line in which the error occurred. For example, in the simple WSH script:On Error Resume Next x = 10 y = 0 z = x / y Alert za “Cannot divide by Zero” error is generated on the fourth line of code because the value of y is 0. Bu
provides a tutorial example on how to use the 'On Error Resume Next' statement to turn on error handling flag. You can use Err.Number > 0 to test if there is any runtime error has been raised or not. We have seen what happens when the error handling flag is turned off in the previous section. Now let's see how the "On Error Resume Next" statement should be used: By default, the error handling flag is turned off. You can turn on the error handling flag at time your want by entering the "On Error Resume Next" statement. Once the error handling flag is turned on, execution will not be stopped when a runtime error occurs. You can use the condition of (Err.Number>0) to determine a runtime error has occurred or not. If a runtime error has occurred, use Err object properties to get more information about the error: Err.Number - "Err" object property containing the error code. Err.Description - "Err" object property containing the error description. Err.Source - "Err" object property containing error source identification. I have modified the VBScript example used in the previous section to try to check the "Err" object by myself with the error handling flag turned on:
Run this example code in IE, you will get: There is no error at this time. Before statement: x = 1/0 Before statement: y = CInt(777777) Before statement: z = 1 + "2nd" End of test A runtime error has occurred: Err.Number = 13 Err.Description = Type mismatch Err.Source = Microsoft VBScript runtime error The output confirms that: When CheckError() was called at the beginning, Err.Number is 0, indicating that there is no runtime error. When the first runtime error occurred on statement, x = 1/0, execution continued because the error handling flag was turned on. When the secon