VBScript hangs when launching batch file with WShell.Script Run

Question

During an install of PostgreSQL 9.1.2 on my Windows 7 64-bit Home Premium box, the installation hung. After a long furious search I discovered the problem was that an installer VB Script was hung waiting for a batch file to complete in a hidden window.

I isolated the problem to the following line of code:

Dim objShell
Set objShell = WScript.CreateObject("WScript.Shell")
objShell.Run "hello.bat", 1, True

(where 1 sets WindowStyle to Visible and True waits for completion). The Run call had launched the command prompt but was not executing the batch file. Thus, it would never complete.

I solved the problem by launching cmd.exe instead of the batch file directly, according to numerous online sources:

objShell.Run "%COMSPEC% /c hello.bat", 1, True

Since the fix is buried in the PostgreSQL installer (and I've submitted a bug report), I can only work around the problem unless the installer is modified.

But my main questions are:

Why does the first call hang?
Why use %COMSPEC% instead of calling the batch directly?

In regards to #2, could this be because executing a .bat directly makes an assumption that the default action associated with a .bat file is to execute it? I've in the past (on other machines) changed this default action to 'Edit'. And if I'd done that, I would have hung the PostgreSQL installer as well! (I imagine)

The batch file executes normally on other machines. So there is something weird on this one laptop. So in regards to #1, I need to figure out why this one laptop is different. I should note that there are some weird behaviors with batch files on this machine (one which I just noticed):

The context menu actions contain only "Open" and are missing "Edit", "Run", "Run As"
Double-clicking a batch file opens a command prompt but does not execute the batch file

I just noticed #2 while writing this. Clearly the default action for .bat is messed up. Yesterday I nearly bricked my computer removing Context Menu Handlers from my registry as recommended by several sites trying to restore my "Edit", "Run", etc. entries.

Any advice on questions 1 and 2 would be appreciated.

Thanks, Eric

I've solved the problem, and will post the answer in 7 hours (new user, sorry). Basically I had to delete this key: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.bat as noted [here](http://help.lockergnome.com/windows/BAT-File-Association-Broken--ftopict514456.html) — cod3monk3y, Jan 27 '12 at 20:08

score 4 · Accepted Answer · answered Jan 28 '12 at 04:41

The problem was an HKCU override on .bat which created an association to cmd.exe, as noted on this wonderful post. Additional help was found here.

My registry looked like this:

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.bat
    \OpenWithList
        (Default)   REG_SZ    (value not set)
        a           REG_SZ    NOTEPAD.EXE
        MRUList     REG_SZ    a
    \OpenWithProgids
        (Default)   REG_SZ    (value not set)
        batfile     REG_NONE  (zero-length binary value)
    \UserChoice
        (Default)   REG_SZ    (value not set)
        Progid      REG_SZ    (Applications\cmd.exe)

Removing the entire .bat entry fixed everything. All context menu items were restored properly (Open, Edit, Print, Run as Administrator, and Troubleshoot Compatability) and double clicking on the batch file executed the batch.

The .bat key re-generated automatically sometime after I deleted it and double-clicked my test batch file. This automatically generated entry was:

HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.bat
    \OpenWithList
        (Default)   REG_SZ    (value not set)
    \OpenWithProgids
        (Default)   REG_SZ    (value not set)
        batfile     REG_NONE  (zero-length binary value)

Ultimately it was the \UserChoice key that was causing my problem. So I'm all cleared up now. My test scripts run properly and I re-installed PostgreSQL from scratch and the install went smoothly.

E

+1 for figuring it out on your own & sharing a detailed solution. — Tomalak, Jan 30 '12 at 09:32

score 0 · Answer 2 · answered Jan 27 '12 at 20:00

The 1st call launches a window that remains open until something tells it to close. Prsumably hello.bat terminates with an EXIT command, which would of course close the window, and your installation can then continue on its way.

But hello.bat fails to run on your one machine, so of course the window never closes, and your installation hangs.

The 2nd call through %COMSPEC% is opening a window and running CMD.EXE with the /C "command" option. The specifiation for the /C option states that CMD.EXE will terminate once the "command" completes (or fails). Your "command" is "hello.bat". Closure of the window is no longer dependent on an EXIT command in the hello.bat file. The window will close even if hello.bat fails to run.

Thanks for the input dbenham. hello.bat was a simple "echo hello > _hello.txt" with no explicit EXIT. The issue was that hello.bat wasn't actually called. The command prompt came up but the batch file wasn't running. It wasn't that the bat file *failed* while running; it wasn't called at all! Re: your second point-- A batch file will exit even without an explicit EXIT command. If the batch file was running and hung, cmd.exe /c would still hang waiting for the command to complete. My issue turned out to be a file extension override (see my own answer). Thanks for your input, though! — cod3monk3y, Jan 28 '12 at 04:44

VBScript hangs when launching batch file with WShell.Script Run

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