Programming Forums > Application Development > C++

badbasser98 · May 12th, 2006, 10:03 AM

How hard would it be to implement a program to run in the background and watch a specific file to see if changes are made to it. Then to display a MessageBox when that happens. Incase its needed this will be for WinXP Pro.

I have created an Internal Support Utility for us to track support calls from our employees and saves the info in a .DAT file (data can be added, edited, or deleted). I wanted to make an extension of that by making a separate program that only allows data entry to the file to place on the users PC's. They can add a "service call" and I would like to know when an addition is made. I know I could just open the program and look at the file to see if there are any new entries. But I believe it would be much more efficient if a notification was presented when a change was made. How hard would this be to do. Or is it even possible?

Thanks,
-BB98

InfoGeek · May 12th, 2006, 10:08 AM

You can check the time stamp of the file. It should be fairly simple.

Infinite Recursion · May 12th, 2006, 10:14 AM

Yes, it is possible...Pizentios and I were working on a similar script, written in Perl, for Linux yesterday.

I modified that script a bit to end up with a monitoring script to notify me when a file changes, in which the changes include certain keywords. It is basically just 'tail'ing the file and parsing the lines. There is about a 10 second turn-around-time... Works fine in Linux, haven't tested it in Windows, but with a bit of modification you should be able to get it to work in Windows or at the very least, take the logic and apply it to a more "windows friendly" language.

(Toggle Plain Text)

#!/usr/bin/perl
 
use File::Tail;
 
$name = "/var/log/nogo.log";
 
$keyword = "denied";
 
$file=File::Tail->new(name=>$name, maxinterval=>10, adjustafter=>7);
while (defined($line=$file->read))
{
   $check = index($line, $keyword);
   if ($check > 0)
   {
	  print "[WARNING]: Unauthorized Access. -> $line\n";
   }
}

Edit: InfoGeek's idea would probably be an easier solution in Windows. Just create a program that will check the file's timestamp, if it has been modified X minutes from specified interval, then send a notification. You could put the program in a scheduled task to make it repeat on a certain time during the day.

The Dark · May 12th, 2006, 12:04 PM

Under Windows you can also use the directory change notification functions documented here

badbasser98 · May 12th, 2006, 3:50 PM

hmm.. I'll look into that.

Thanks,
-BB98

badbasser98 · May 12th, 2006, 4:34 PM

Ok I've got a question regarding FindFirstChangeNotification...

It says when it fails it returns INVALID_HANDLE_VALUE. I guess I don't understand what it returns when it is successful but does not find a change. Or would that be a failure?

DaWei · May 12th, 2006, 4:55 PM

If I send you for a gallon of milk and you can't find any, is that a failure? If there is none to be found, is that a failure?

nnxion · May 12th, 2006, 5:16 PM

Have you fully read this page? If so you must have tried to use GetLastError. What did that return?

The Dark · May 12th, 2006, 7:41 PM

Quote:

Originally Posted by badbasser98

Ok I've got a question regarding FindFirstChangeNotification...

It says when it fails it returns INVALID_HANDLE_VALUE. I guess I don't understand what it returns when it is successful but does not find a change. Or would that be a failure?

The FindFirstChangeNotification function does not check for changes immediately, it creates a handle to an object that you can "wait" for using the WaitForSingleObject or WaitForMultipleObject functions. When the wait function returns, then either a change has happenned, or a timeout has occurred.
When you use this function, you don't have to poll for changes every so often, you just set up the notification, then call the wait function, when the wait function returns, a change has happenned. This way, your program doesn't take any CPU while waiting.

badbasser98 · May 17th, 2006, 9:08 AM

Well, I got the program working. It was surprisingly easy. I think I was trying to make it harder than what it was.

Thanks for all the help.
-BB98

May 12th, 2006, 10:03 AM	#1
badbasser98 Hobbyist Programmer Join Date: Mar 2005 Location: United States Posts: 124 Rep Power: 4	changes to file. How hard would it be to implement a program to run in the background and watch a specific file to see if changes are made to it. Then to display a MessageBox when that happens. Incase its needed this will be for WinXP Pro. I have created an Internal Support Utility for us to track support calls from our employees and saves the info in a .DAT file (data can be added, edited, or deleted). I wanted to make an extension of that by making a separate program that only allows data entry to the file to place on the users PC's. They can add a "service call" and I would like to know when an addition is made. I know I could just open the program and look at the file to see if there are any new entries. But I believe it would be much more efficient if a notification was presented when a change was made. How hard would this be to do. Or is it even possible? Thanks, -BB98 __________________ Learning to use C++ and loving every minute of it.

May 12th, 2006, 10:08 AM	#2
InfoGeek Professional Programmer Join Date: Jun 2005 Location: India, The great. Posts: 435 Rep Power: 4	You can check the time stamp of the file. It should be fairly simple. __________________ PFO - My daily dose of technology.

May 12th, 2006, 10:14 AM	#3
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,473 Rep Power: 8	Yes, it is possible...Pizentios and I were working on a similar script, written in Perl, for Linux yesterday. I modified that script a bit to end up with a monitoring script to notify me when a file changes, in which the changes include certain keywords. It is basically just 'tail'ing the file and parsing the lines. There is about a 10 second turn-around-time... Works fine in Linux, haven't tested it in Windows, but with a bit of modification you should be able to get it to work in Windows or at the very least, take the logic and apply it to a more "windows friendly" language. (Toggle Plain Text) #!/usr/bin/perl use File::Tail; $name = "/var/log/nogo.log"; $keyword = "denied"; $file=File::Tail->new(name=>$name, maxinterval=>10, adjustafter=>7); while (defined($line=$file->read)) { $check = index($line, $keyword); if ($check > 0) { print "[WARNING]: Unauthorized Access. -> $line\n"; } } #!/usr/bin/perl use File::Tail; $name = "/var/log/nogo.log"; $keyword = "denied"; $file=File::Tail->new(name=>$name, maxinterval=>10, adjustafter=>7); while (defined($line=$file->read)) { $check = index($line, $keyword); if ($check > 0) { print "[WARNING]: Unauthorized Access. -> $line\n"; } } Edit: InfoGeek's idea would probably be an easier solution in Windows. Just create a program that will check the file's timestamp, if it has been modified X minutes from specified interval, then send a notification. You could put the program in a scheduled task to make it repeat on a certain time during the day. __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

May 12th, 2006, 3:50 PM	#5
badbasser98 Hobbyist Programmer Join Date: Mar 2005 Location: United States Posts: 124 Rep Power: 4	hmm.. I'll look into that. Thanks, -BB98 __________________ Learning to use C++ and loving every minute of it.

May 12th, 2006, 4:34 PM	#6
badbasser98 Hobbyist Programmer Join Date: Mar 2005 Location: United States Posts: 124 Rep Power: 4	Ok I've got a question regarding FindFirstChangeNotification... It says when it fails it returns INVALID_HANDLE_VALUE. I guess I don't understand what it returns when it is successful but does not find a change. Or would that be a failure? __________________ Learning to use C++ and loving every minute of it.

May 12th, 2006, 12:04 PM	#4
The Dark Expert Programmer Join Date: Jun 2005 Posts: 893 Rep Power: 4	Under Windows you can also use the directory change notification functions documented here

May 12th, 2006, 4:55 PM	#7
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	If I send you for a gallon of milk and you can't find any, is that a failure? If there is none to be found, is that a failure? __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

May 12th, 2006, 5:16 PM	#8
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	Have you fully read this page? If so you must have tried to use GetLastError. What did that return? __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

May 17th, 2006, 9:08 AM	#10
badbasser98 Hobbyist Programmer Join Date: Mar 2005 Location: United States Posts: 124 Rep Power: 4	Well, I got the program working. It was surprisingly easy. I think I was trying to make it harder than what it was. Thanks for all the help. -BB98 __________________ Learning to use C++ and loving every minute of it.

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Programming Forums > Application Development > C++

changes to file.