Question

I’m trying an example from M$ site regarding calling Windows Update programatically.

'http://msdn.microsoft.com/en-us/library/aa387102%28VS.85%29.aspx
'http://msdn.microsoft.com/en-us/library/aa386526%28v=vs.85%29.aspx

Set updateSession = CreateObject("Microsoft.Update.Session")
Set updateSearcher = updateSession.CreateupdateSearcher()

WScript.Echo "Searching for updates..." & vbCRLF

Set searchResult = updateSearcher.Search("IsInstalled=1 and Type='Software'")

On executing the last line, if your network is broken, I’ll see on CMD window:

C:\wu-script\wu-install.vbs(9, 1) (null): 0x8024001F

It seems like updateSearcher.Search throws an exception and the whole script exits. How to catch this exception?

I’m not very familiar with VBScript. Please provide a quick hint or a reference URL.

Answer 1

You should use On Error statement to handling VBScript errors.

'...
'...
On Error Resume Next 'enable error handling
Set searchResult = updateSearcher.Search("IsInstalled=1 and Type='Software'")
If Err.Number <> 0 Then
    'right, this is a catch block :/
    WScript.Echo "error!"
    'WScript.Echo Err.Description
    'more : http://msdn.microsoft.com/en-us/library/a3c123d4(v=vs.85).aspx
End If
On Error Goto 0 'disable error handling

As you can see, catching error is too troublesome in VBScript. However, could also use javascript and its try-catch.
A sample WSF package based on the script that you gave.

wu-install.wsf

<?xml version="1.0" ?>
<package>
 <job id="Update">
  <script language="JScript">
   <![CDATA[
        //http://msdn.microsoft.com/en-us/library/aa387102%28VS.85%29.aspx
        //http://msdn.microsoft.com/en-us/library/aa386526%28v=vs.85%29.aspx
        var updateSession = WScript.CreateObject("Microsoft.Update.Session");
        var updateSearcher = updateSession.CreateupdateSearcher();
        WScript.Echo("Searching for updates...");
        try {
            var searchResult = updateSearcher.Search("IsInstalled=1 and Type='Software'");
        } catch(err){
            WScript.Echo("error!");
            //WScript.Echo(err.message);
            // more : http://msdn.microsoft.com/en-us/library/dww52sbt(v=vs.85).aspx
        }
   ]]>
  </script>
 </job>
</package>

Runing with the cmd:

C:\wu-script>cscript wu-install.wsf