CreateProcess by LabVIEW

[Zeck]

I am trying to use WinAPI CreateProcessA (kernel32.dll) for future use. I am getting return value 0. What am I doing wrong?

LabVIEW 7.1, XP SP2.

[Lycangeek]

A few comments to answer

1. You can always call GetLastError() in the Win32 API for any function that returns a boolean to indicate pass or fail. It will give you the actual error code, which you can then look up.

2. LV Clusters and C structures are not the same thing. You are trying to pass a pointer to a LV cluster (via the void*) directly to the Win32 API that is expecting a C structure - it is probably getting garbage. Similar issue for the data coming out. In fact, you might end up with corrupted memory...I don't recommend doing this.

3. A much easier approach is to use the .NET System.Diagnostics.Process class, which lets you do the same thing but has full data support in LabVIEW 7.x.

[PJS]

Additionally, I think that your startupinfo cluster is missing two elements.  If memory serves they are dwXSize and dwYSize located between dwY and dwXCountChars.

[Zeck]

Thanks a lot.

I will check it one more time and definitelly will check Process Class from .NET.

Zeck

P.S. 1)  I was trying to use GetLastError() with no luck, it shows NoErorr.

        2)  I created header file to see how LV converts structure and i found that LV is smart enouph to 

              produces very similar structure to the code provided by MSDN.

[Lycangeek]

1. Strange! I have no response to that one...

2. Yes, it often is close but remember that "often" isn't "always". At a minimum, for example, LV data structures are 1-byte aligned where Win32 structures are 4-byte aligned. So a structure such as

struct Oops {

   int abc;

   byte def;

   int ouch;

};

Have different memory layouts, even if the structure definitions are the same.

Let me know if you have any questions with the .NET API's...

[Zeck]

Thanks you.

I was thinking about It, but wanted to check with much more advanced people.

So, as I understood, I really have concentrate on .Net. I have never worked with it so, let me read about it and see some examples first.

Thanks again, I will return as I have something or stock with something.

Zeck

[Zeck]

.Net is working for me.

Thank you for help.

Zeck

[Zeck]

Here is vi with CreateProcessA and GetLastError working.

In order to properly handle stdIn and stdErr in .NET Microsoft recommends to use second (or another) thread but I

could not get enough Information how to do that. Any idea?

Thank you.

Zeck

[Lycangeek]

You actually will do it very differently in LV than you would in C#, simply because of the way LV handles threads.

Exactly how best to handle this is going to depend on what you want to do. For example, if you simply want a thread to sit and read from stderr, the easiest thing to do is create a subVI that takes in the .NET refnum for the process and reads stderr. So I would recommend something like

a. Create an instance of the process class and start the process via .NET.
b. Create a subVI that does the stdin, stdout work - the main stuff you are planning on. Set the VI execution thread to "other 1"
c. Create a subVI that does the stderr work. Set the VI execution thread to "other 2"
d. Execute the two subVI's in parallel - make sure you don't have anything that would serialize the execution of the two subVIs.

Does that make sense?

[terrill]

I decided to try the .net approach. I have never used .net before. I placed a constructor node down but coud not link it to the System.Diagnostics.Process class. I found the class in the list but there are no constructors listed. Could someone help me get a constructor that would let me get to the process class. Thanks.