Error Handling In Vbscript Tutorial
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Vbscript Error Handling Best Practices
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Vbscript Error Handling Line Number
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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
Vbscript On Error Continue
Is Structured Conventions in This Book How To Contact Us I. The Basics 1. Introduction vbscript clear error 2. Program Structure 3. Data Types and Variables 4. Error Handling and Debugging 5. VBScript with Active Server Pages 6. Programming Outlook vbscript goto 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 https://technet.microsoft.com/en-us/library/ee692852.aspx 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 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 https://www.safaribooksonline.com/library/view/vbscript-in-a/1565927206/ch04s02.html 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. 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
of system administration. However in doing this I came across a gap in the existing Microsoft documentation and in many of the VBscripting books http://blog.ellisons.org.uk/article-1 available(1) . None seem to give a clear and coherent explanation of how error processing works in VBscript. I think that I’m still a competent VBscript programmer, yet as I dug deeper I found some features that surprised me and that most of our script coders knew even less about this than I did! However, if you think that you already understand how error handling works in error handling VBscript, then try your knowledge on the following example. Look at the code and write down the error codes that it outputs up to the point where it fails, then compare your list to the answers at the end of this paper(5). I might warn you that I have yet to find anyone who gets it 100% right on the first attempt. On Error Resume Next ' Note handling in vbscript that 1/0 generates error 11 -- division by zero ' Note that a(2) generates error 9 -- subscript out of range a = Array (0,1) b = 1/a(0) : Wscript.Echo "(a) = ", Err.Number Err.Clear c = a(2) : Wscript.Echo "(b) = ", Err.Number b = 1/c : Wscript.Echo "(c) = ", Err.Number b = 1/a(2) : Wscript.Echo "(d) = ", Err.Number Wscript.Echo "(e) =", b , Err.Number Wscript.Echo "(f) = ", a(2), Err.Number b = a(0): Wscript.Echo "(g) = ", Err.Number Blah a, 2, true, false : Wscript.Echo "(h) = ", Err.Number Blah a, 2, false, true : Wscript.Echo "(i) = ", Err.Number Blah a, 2, false, false : Wscript.Echo "(j) = ", Err.Number Blah a, 1, true, false : Wscript.Echo "Overall Status =", Err.Number Sub Blah(a, i, trap, cont) If trap Then On Error Goto 0 If cont Then On Error Resume Next b = a(i) c = 1/b End Sub So this paper is really essential reading for anyone who uses VBscript for the automation of server or client administration, ASPs or any other purpose. It provides documentation and guidance on how to code to avoid the pitfalls whilst utilizing the strengths of VBscript error handling.