Re: Automatically monitoring a file written by a 3rd party program.

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Fri, 8 Aug 2008 19:03:37 -0400
"TonyG" <> wrote in message

I need to monitor a 3rd party program that is running on our computer
system. This 3rd party program does not output the data I need in any
convenient method like a COM port or socket. The only thing it does is
output records to a log text file and this can happen at the rate of many
records per minute.

So I am thinking about having my program read the 3rd party program's log
file once a minute. The program would read in the new message entries and
then use the data.

Obviously I can keep track of the old file position and jump to that point
the next time I read the file. Is there any fancy methods I don't know

What are the ways I can tackle this problem? --- Is there a way I can
register my program to receive the file changes? Are there operating
system calls that can tell me when the file has been modified? Can the
operating system automatically route file changes to me?

Also will I run into problems if I am trying to read the file when the
other program is in the middle of writing the file and visa-versa.

You can get notifications when the file changes - see
FindFirstChangeNotification. There is no way you can receive the changes -
you must read the file for that.

Whether or not there will be problems reading it while the other program is
writing it depends on the file sharing flags used by the other program. If
you don't have source to the other program you'll just have to try it and

Scott McPhillips [VC++ MVP]

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