C / C++ / MFC

Re: how to idenitify whether process is running or not

16-Aug-02 3:58

Hi
I started 2 processes in my app. and now every one second i want to see if these processes are still running. Coud anyone please tell me how i can get the status of a process to see whether it is running or has been terminated?

thanks

Tomasz Sowinski16-Aug-02 4:04

Re: how to idenitify whether process is running or not

16-Aug-02 4:04

tcuong wrote:
now every one second i want to see if these processes are still running

Why 'every one second'? Can't you create a thread which waits for process termination with WaitForSingleObject, then posts a message?

Tomasz Sowinski -- http://www.shooltz.com

Never argue with an idiot, he'll bring you to his level and beat you with experience.

tongc16-Aug-02 6:04

Re: how to idenitify whether process is running or not

16-Aug-02 6:04

this is to monitor if the processes are running or not? It is just an excercise to get myselft familiar with Win32 programming.

First i create 5 process namely notepad.exe . Then i have to monitor that how many of these processes are running every 1 second. I've attempted many ways to do it but i failed. This is how i did it.

<br />
void main()<br />
{<br />
//	HANDLE handle;<br />
	STARTUPINFO startUpInfo[5];<br />
	PROCESS_INFORMATION proInfo[5];<br />
	BOOL success;<br />
	HANDLE proHandle[5];<br />
	INT i;<br />
	INT runningProcess = 5;<br />
	CHAR appName[100];<br />
	<br />
	<br />
<br />
	<br />
	strcpy(appName, "c:\\windows\\notepad.exe");<br />
<br />
<br />
	//DWORD status[5];<br />
	<br />
	<br />
	for(i = 0; i <5; i++)<br />
		GetStartupInfo(&startUpInfo[i]);<br />
	<br />
<br />
	//Create process<br />
	for(i = 0; i < 5; i++)<br />
	{<br />
		success = CreateProcess(appName, 0, 0, 0, FALSE, 0, 0,0,&startUpInfo[i], &proInfo[i]);<br />
		<br />
		if(!success)<br />
			cout <<" Error creating process: "<< GetLastError() <<endl;<br />
		<br />
		cout << "The process ID is " << proInfo[i].dwProcessId << endl;<br />
	}<br />
<br />
	for(i = 0; i <5; i++)<br />
	{<br />
		proHandle[i] = proInfo[i].hProcess;<br />
	}<br />
<br />
while (WaitForMultipleObjects(5, proHandle, TRUE, 1000) == WAIT_TIMEOUT)<br />
	{<br />
		for(i = 0; i < 5; i++)<br />
		{<br />
			if(proInfo[i].hProcess == NULL)<br />
				runningProcess--;<br />
<br />
		}<br />
		<br />
	<br />
		printf(" %d ", runningProcess);		 <br />

I know that this code may look silly to some of you but instead of laughing, please guide me to the right direction. Thanks

Tomasz Sowinski16-Aug-02 7:04

Re: how to idenitify whether process is running or not

16-Aug-02 7:04

tcuong wrote:
instead of laughing, please guide me to the right direction.

Nobody laughs at you. Seriously.

If you insist on using WaitForMultipleObjects:
- proInfo[i] will not be set to NULL when process terminates
- setting 3rd argument to TRUE causes WaitForMultipleObjects to exit only if timeout occured or *all* processes have terminated. This is obviously not what you're looking for.

Tomasz Sowinski -- http://www.shooltz.com

Never argue with an idiot, he'll bring you to his level and beat you with experience.

Daniel Lohmann16-Aug-02 13:10

Daniel Lohmann

16-Aug-02 13:10

tcuong wrote:

while (WaitForMultipleObjects(5, proHandle, TRUE, 1000) == WAIT_TIMEOUT)
{
    for(i = 0; i < 5; i++)
    {
        if(proInfo[i].hProcess == NULL)
            runningProcess--;
    }
    printf(" %d ", runningProcess);
}

This code looks neither silly nor anybody wants to laugh on you, really!

First I thought the problem is the TRUE parameter for bWaitAll in your call to WaitForMultipleObjects(), (which is a common mistake) but then I realized that you want to loop until all handles reached signaled state (a process or thread handle becomes signaled if it terminates). Quite clever!

Your problem is, that a signaled handle is not set to NULL, it is still present. Therfore your process counter is never decremented. If you change the line

if(proInfo[i].hProcess == NULL)
    runningProcess--;

// check if handle is signaled (which means process has terminated)
if( WaitForSingleObject( proInfo[i].hProcess, 0 ) == WAIT_OBJECT_0 )
    runningProcess--;

it should work. (Note that I just wrote the above from scratch and did not test it Blush | :O

)

However, your description intents that you want to check the status exactly every 1 second. The above checks it at least every 1 second. This is because the WaitForMultipleObjects() returns if either a handle becomes signaled or the timeout elapsed. Of course, this is a negligible detail in almost any case, but hey, you wrote you want to learn how to solve it with Win32 API Big Grin | :-D

One idea is to use Sleep() instead of WaitForMultipleObjects():

while ( runningProcess > 0)
{
    for(i = 0; i < 5; i++)
    {
        if( WaitForSingleObject( proInfo[i].hProcess, 0 ) == WAIT_OBJECT_0 )
            runningProcess--;
    }
    printf(" %d ", runningProcess);
    Sleep( 1000 );
}

BTW: If you bracket your code postings to the forum with <pre> and </pre> tags, the formatting will survive. This would makes it much more comfortable to read it.

--

Daniel Lohmann

http://www.losoft.de
(Hey, this page is worth looking! You can find some free and handy NT tools there Big Grin | :-D

)

Re: how to idenitify whether process is running or not

tongc16-Aug-02 13:51

Re: how to idenitify whether process is running or not

16-Aug-02 13:51

Daniel! This is a big help! I really appreciate it! Thank you very much!

Best Regard

tongc16-Aug-02 14:57

Re: how to idenitify whether process is running or not

16-Aug-02 14:57

Hi Daniel! I've got it. I just post it up here to let you know that with your help. FULL credit to you!!! Smile | :)

BOOL flag[5];
	for(i = 0; i < 5; i++)
		flag[i] = true;

	while (WaitForMultipleObjects(5, proHandle, TRUE, 1000) == WAIT_TIMEOUT)
	{
		
			if( WaitForSingleObject( proInfo[0].hProcess, 0 ) == WAIT_OBJECT_0 && flag[0] == true)
			{
				runningProcess--;
				flag[0] = false;
			}
			
			if( WaitForSingleObject( proInfo[1].hProcess, 0 ) == WAIT_OBJECT_0 && flag[1] == true)
			{
				runningProcess--;
				flag[1] = false;
			}

			if( WaitForSingleObject( proInfo[2].hProcess, 0 ) == WAIT_OBJECT_0 && flag[2] == true)
			{
				runningProcess--;
				flag[2] = false;
			}

			if( WaitForSingleObject( proInfo[3].hProcess, 0 ) == WAIT_OBJECT_0 && flag[3] == true)
			{
				runningProcess--;
				flag[3] = false;
			}

			if( WaitForSingleObject( proInfo[4].hProcess, 0 ) == WAIT_OBJECT_0 && flag[4] == true)
			{
				runningProcess--;
				flag[4] = false;
			}
				
		
		printf(" %d ", runningProcess);		 
		
	}

This might look lengthy and messy for a moment but i think i can tight it in a loop!! Thanks!!!!

Also thanks to Tomasz !! I greatly appreciate it!!!

tongc16-Aug-02 15:02

Definition of Serialization

16-Aug-02 15:02

And this is the code after i've shortened it!!!

while (WaitForMultipleObjects(5, proHandle, TRUE, 1000) == WAIT_TIMEOUT)
	{
		for(i = 0; i< 5; i++)
		{
			if( WaitForSingleObject( proInfo[i].hProcess, 0 ) == WAIT_OBJECT_0 && flag[i] == true)
			{
				runningProcess--;
				flag[i] = false;
			}
		}
				
		printf(" %d ", runningProcess);		 
		
	}

Thanks for the tips Daniel (remember the pre tag) Smile | :)

Nick Parker16-Aug-02 3:56

16-Aug-02 3:56

Could someone give me a clear definition of serialization. The way I see it is that it is a method to transfer data from memory to file. I may be completely wrong here and I would really like to know the correct meaning. Thanks.

Nick Parker

Tomasz Sowinski16-Aug-02 4:08

16-Aug-02 4:08

Nick Parker wrote:
The way I see it is that it is a method to transfer data from memory to file.

'From' side: usually, you have an 'object graph' - objects related to each other (parent/child relationships, etc). You need to 'flatten' this structure somehow, because you'll need a serial stream of bytes. See 'To' side.

'To' side: not necessarily file. Just sequential stream of bytes - it may be file, network, another memory location, telepatic transceiver or whatever.

Tomasz Sowinski -- http://www.shooltz.com

Never argue with an idiot, he'll bring you to his level and beat you with experience.

Nick Parker16-Aug-02 4:20

16-Aug-02 4:20

Ok, I think I understand what you are saying. This provides a method to transport the data (generically speaking) from point A to point B, is that correct?

Tomasz Sowinski wrote:
'From' side: usually, you have an 'object graph' - objects related to each other (parent/child relationships, etc). You need to 'flatten' this structure somehow, because you'll need a serial stream of bytes. See 'To' side.

Could you explain this a little more?

Nick Parker

Tomasz Sowinski16-Aug-02 4:29

16-Aug-02 4:29

I'm assuming that you want me to explain the 'object graph' thing.

Imagine that you have CDocument derived class. It usually contains some data. They may be integers, strings, arrays etc. Serializing them is easy - you're just writing/reading their binary representation.

Now - what happens when you have a pointer in your document? What if it points to an object which has a 'backpointer' to document? These objects connected together are called 'object graph'. Any serialization mechanism must be ready to deal with such situation. Two most important points are:

- you may have polymorphic objects and pointers of type 'CYourBaseObject *'. But pointers point to CYourConcreteType1 or CYetAnotherTypeDerivedFromYourBaseObject. On the deserialization side, you want the real type to be preserved.

- you may more than one pointer to the same object. Both sides of operation must be smart enough to serialize object data only once.

Luckily, as an user of MFC or .NET, you don't need to worry about such issues.

Tomasz Sowinski -- http://www.shooltz.com

Never argue with an idiot, he'll bring you to his level and beat you with experience.

Nick Parker16-Aug-02 4:38

16-Aug-02 4:38

This is a flow chart of me trying to follow what you just said:

Tomasz Sowinski wrote:
Imagine that you have CDocument derived class. It usually contains some data. They may be integers, strings, arrays etc. Serializing them is easy - you're just writing/reading their binary representation.

Understood. Smile | :)

Tomasz Sowinski wrote:
Now - what happens when you have a pointer in your document?

Starting to get lost... Unsure | :~

Tomasz Sowinski wrote:
What if it points to an object which has a 'backpointer' to document?

Fully lost now. OMG | :OMG:

Tomasz Sowinski wrote:
These objects connected together are called 'object graph'.

Okay. Smile | :)

Tomasz Sowinski wrote:
Luckily, as an user of MFC or .NET, you don't need to worry about such issues.

Thank goodness, I thought I was going to have to be lost again. Smile | :)

Nick Parker

Tomasz Sowinski16-Aug-02 4:44

16-Aug-02 4:44

Nick Parker wrote:
Now - what happens when you have a pointer in your document?
Starting to get lost...

Quick example:

You have MFC doc/view app. Your doc class is CWidgetDoc. You've defined a CWidget class, which is a base for CBlueWidget, CTriangleWidget and CStereoWidget.

CWidget class has the following member variable:

CWidgetDoc *m_pParentDoc;

In your CWidgetDoc, you store unlimited number of widgets. You're using std::vector for that:

std::vector<CWidget *> m_widgets;

Your users work with the app and create blue/triangle/stereo widgets. m_widgets grows and contains pointers to different types of objects; all they have in common is the base class, CWidget.

There are pointers going from document to widget. There are pointers going from widgets to document. This is simple object graph - with complicated program, you'd have more tangled structure.

Tomasz Sowinski -- http://www.shooltz.com

Never argue with an idiot, he'll bring you to his level and beat you with experience.

Nick Parker16-Aug-02 4:47

16-Aug-02 4:47

Tomasz Sowinski wrote:
There are pointers going from document to widget. There are pointers going from widgets to document. This is simple object graph - with complicated program, you'd have more tangled structure.

Gotcha, thanks Tomasz Smile | :)

Nick Parker