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check the existence of a file.

Question asked by Rapid on Nov 17, 2008
Latest reply on Nov 19, 2008 by odanzy

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Hey guys! i have a question... There is a better way to check the existence of a file?

Currently i have an "Until Break" follow by one "sleep" and then i check the existence of the file by using "System.IO.File.Exists(path);" function.

My problem is that seems this function use to much the CPU.

Thanks for your help.

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jborges3 Nov 17, 2008 4:25 PM
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Hello Rapid,

Your program will check for the existence of this file over and over in an infinite loop. Infinite loops are resource hogs, but the "File Exists?" function alone doesn't bog down your CPU.

Can you please tell us what is it exactly that you are trying to do? We may be better able to help you with suggestions if we understand what you are doing.

When I check for the existence of a file I use the same "File Exists?" function, but I only check once right before I read the file. I've attached a screen image that shows how I use the function. The last blocks of "do something" or "warn user" are just pseudo code blocks to show the idea.

Best regards,
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- VEETestIfFileExists.JPG21.6 KB
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Rapid Nov 18, 2008 4:57 AM
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Yes, you are right... The problem its the infinite loop. ThatÂ´s why i use a "sleep". Because if i donÂ´t use the sleep... The CPU goes to 100%!. Using this Sleep goes to 30% almost every time..

The reason why i use this code... is because i need to check the existence of "done.txt". If the done exist then... i analyze everything... if not.. just wait for the done.txt. Its a synchronization, between two programs...

I made the same code in c++, and the CPU is almost 10% instead of 30%. Just the same, the infinite loop, with a sleep and a function that checks the file. Then i think that may be the "System.IO.File.Exists(path);"

do
{
Sleep (3000);
if (GetFileAttributes(DONEPATH) == INVALID_FILE_ATTRIBUTES)
   {
      cout << "file is missing... " << endl;
    }
else
   {
      cout << "file already exist" << endl;
   }

}while(character != 's');

Maybe... there is a better way... to check if this file exist... I just want to know if i can improve this Vee program. If not... i will to make the same program in C++. I already did it, and works just fine! but... i have a lot of vee programs and it will take me to long to pass everything to c++. So if i can improve this agilent i probably keep with Vee... i already did it... but, i think c++ is faster. So what do you think?

THANKS!! for everything..
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jborges3 Nov 18, 2008 11:23 AM
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Hi Rapid,

I understand the issue now. What is the other program that you are synchronizing between, are they both written in VEE?

The problem is that you are trying to run both programs at the same time, and one of them is an infinite loop, so this loop program slows down the first program. Having some or all of the code in C++ may run faster, but a change to how you're doing things should solve the issue with out any slow down and with out having to translate your code to C++.

May I suggest that you change both programs. Have the first program write the file, then have the 1st program launch the 2nd program just before the 1st program exits. This allows the 2nd program to check the existence of the file only once as an error check, but not over and over as a way to see if the first program is finished.

To implement this in VEE you could write the second program as a function, and have the first program pass the file name to the function so it doesn't have to be hard coded into the processing portion of the program.

Let me know if this makes sense or if you need a hand implementing this,

Best regards,
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Rapid Nov 18, 2008 12:02 PM
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Make sense to me... but... the other program is in Visual Basic. So, i cant do that. If both programs were in VEE... i would make 1 program. Thats why i need to search for this done.txt.

Maybe is the only way to do this. I agree that these is not the best solution for my problem. So i think it would be fine make everything in C++. And that, will make my process faster in every way... because i will not write files anymore..

Thanks!! for everything.
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jborges3 Nov 18, 2008 12:13 PM
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Hi Rapid,

VB should have no problem launching a executable file. If you save your VEE program as a VXE (executable VEE) then your VB code should be able to launch it. This could save you any code re-writing and get rid of the file checking loop.

Best regards,
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Rapid Nov 19, 2008 4:30 AM
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Thats correct to!!... But, i cant lunch the program every time. Because the VB in 1 minute, make 30 done.txt. So.... that would be too slow! don't you think?.

Maybe... the VB aplication, could send a message to the VEE application.. But i don't know how to do it..

Thanks!!
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odanzy Nov 19, 2008 6:40 AM
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You could also call your VB exe from VEE using "I/O->Execute Program". You can have that function block hold off executing anything else until the exit code from the executing program is received. The other option would be to have the program go off and do other things until a specific exit code is received, if required. This should allow you to not even need the "done.txt" file as long as your program does not return until after everything has completed.
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