Error Handling In Vbscript
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Error Handling In Vbscript Tutorial
IT professionals For technical support Support offerings More support Microsoft Premier Online TechNet Forums MSDN Forums Security Bulletins & Advisories Not an IT pro? Microsoft Customer Support Microsoft Community Forums United States (English) Sign in Home Library Wiki Learn Gallery Downloads Support Forums Blogs We’re sorry. The content you requested has been removed. You’ll be auto redirected in 1 second. Script Center VBScript Doctor Scripto’s Script Shop Doctor Scripto’s Script Shop To Err Is VBScript – Part 1 To Err Is VBScript – Part 1 To Err Is VBScript – Part 1 Bring in da Subs, Bring in da Funcs - Building scripts with procedures Controlling pest-ware with asynchronous event monitoring Greg Smacks Down Procedures Inventorying Windows XP Service Packs - Part 1 Inventorying Windows XP Service Packs - Part 2 Inventorying Windows XP Service Packs - Part 3 - Scripting the Rollout It's 2 a.m. Do you know where your processes are? It's 2 a.m. Do you know where your processes are? - The Sequel Metering Application Usage with Asynchronous Event Monitoring Out of Sync: The Return of Asynchronous Event Monitoring To Err Is VBScript – Part 1 T
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 vbscript on error continue talk about it a bit for the next few days. Today, I want
Vbs On Error Goto
to very carefully describe what the error handling semantics are in the language, because there is some confusion if err.number 0 then over how exactly it works. There are two statements that affect error handling in VBScript: On Error Resume NextOn Error Goto 0 The meaning of the first seems clear -- if https://technet.microsoft.com/en-us/library/ee692852.aspx you get an error, ignore it and resume execution on the next statement. But as we'll see, there are some subtleties. But 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 https://blogs.msdn.microsoft.com/ericlippert/2004/08/19/error-handling-in-vbscript-part-one/ 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 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 ba
VBScript in a Nutshell by Matt Childs... Published by O'Reilly Media, Inc. VBScript in a Nutshell Preface Why This Book? Who Should Read This Book? How This Book Should Be Used How This Book Is Structured Conventions in This Book How https://www.safaribooksonline.com/library/view/vbscript-in-a/1565927206/ch04s02.html To Contact Us I. The Basics 1. Introduction 2. Program Structure 3. Data Types and Variables https://www.safaribooksonline.com/library/view/vbscript-in-a/1565927206/ch04.html 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 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 error handling 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 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 error handling in 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. But because you’ve placed the On Error statement in line 1, program execution continues with line 5. The problem with this is that when an error is generated, the user is unaware of it; the only indication that an error has occurred is the blank Alert box (from line 5) that’s displayed for the user.TipA particular On Error statement is valid until another On Error statement in the line of execution is encountered. This means that if Function A contains an On Error statement, and Function A calls Function B, but Function B does not contain an On Error statement, the error handling from Function A
Published by O'Reilly Media, Inc. VBScript in a Nutshell Preface Why This Book? Who Should Read 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 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 Language Reference III. Appendixes A. Language Elements by Category B. VBScript Constants C. Operators Index Colophon Chapter 4. Error Handling and DebuggingErrors, bugs, and therefore debugging are a part of life for a programmer. As the saying goes, if you haven’t made any mistakes, then you aren’t trying hard enough.Dealing with errors actually involves two very different processes: error handling and debugging. Error handling is a combination of coding and methodology that allows your program to anticipate user and other errors. It allows you to create a robust program. Error handling does not involve weeding out bugs and glitches in your source code, although some of the error handling techniques covered in this chapter can be used to great advantage at the debugging stage. In general, error handling should be part of your overall program plan, so that when you have an error-free script, nothing is going to bring it to a screeching halt. With some sturdy error handling in place, your program should be able to keep running despite all the misuse that your users can—and certainly will—throw at it.The following ASP page illustrates some simple error handling: