See what process is using a file in Mac OS X

Question

I would like to be able to track a file and see which process is touching that file. Is that possible? I know that I can see the list of open processes in activity monitor

Answer 1

The faster way is:

$ lsof [path_to_file]

This solution doesn't require the root password and gives you back the following, clear, result:

COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF     NODE NAME
Finder     497  JR7   21r   REG    1,2   246223 33241712 image.jpg
QuickLook 1007  JR7  txt    REG    1,2   246223 33241712 image.jpg