monitoring and printing a file using stat commands.

I am trying to write a program that would monitor the file and print each time it changes.

I am trying to compare the contents of the file using the "stat" commands - st_mtime, st_atime and also st_size.

Can anybody tell me if I have to approach this program by using stat commands like this or is there any other approach to the above problem?

thanks

you could use diff, or checksum (called md5sum in linux, methinks).
Using diff requires a copy of the file(s) which could lead to problems with hard disk space depending on the size and number of files.
With checksum you can save the results in a small file, but your processor overhead could be greater, again depending on the number and size of the files.

What are you trying to do? If security is your goal, I believe the times are can be manipulated, and size checks are certainly not a clear indication of manipulation either.

-Steven

You should stat the file and look at mtime. "tail -f" works that way. You might look at the source code for tail to see how it works.

I am not so experienced in Unix and am trying to learn it these days.
I am trying to write this proram for a small file first to see how the logic works. But at the same time, I realized that diff command would create problems with the disk space for larger files. So I wanted to know, if stat structure works fine for this kind of a problem.

Thanks a lot for writing back to me guys, I will let you know if I face any more problems.

please help me again

I am trying to execute the above program .

The problem is when I am exeuting the file with
a.out monitored_filename
it doesnt show me anything on the screen. I am not aware of how should I change the monitored_file so that it follows the loop and prints something. How shuld I call that program to modify it. I tried to search it in the Unix book , but couldnt find anything.

if(fstat(filedes,&stbuf) == -1)
{
printf("couldnt stat \n");
exit(1);
}
for(;
{
if(stbuf.st_mtime != last_time)

printf("file modified");
last_time = stbuf.st_mtime;
sleep(60);
fstat(filedes,&stbuf);
}
}

consider using stat() not fstat() because fstat requires that you have the file open.
try something like this: