At 2:19 PM -0400 10/13/07, Garry T. Williams wrote: >On Saturday 13 October 2007 13:22:44 Tony Nelson wrote: >> At 7:55 AM -0400 10/13/07, Garry T. Williams wrote: >> >On Thursday 11 October 2007 08:50:31 FS wrote: >> >> I have a need to track changes to a file being made in real-time. >> > >> >Curtis mentioned inotify(7). Here's a small sample program using this >> >interface. >> >> AFAICT, inotify cannot solve the OP's problem. He already knows the file. >> He needs to know /where/ and /what/ changed in the file. inotify can >> optimize the actual solution so it won't need polling. > >Yes. Inotify handles the when (you're called back whenever a file is >modified). The application can then determine the what. > >I don't know about the where. Not sure I understand what you mean by >that. > >Of course, if we knew more of the detailed requirements and data >structures, we could design the "diff" part of the application too. I >assume the OP is capable of handling that part. I think you assume wrong. Here is the OP, with a fairly detailed description of the problem to be solved: At 8:50 AM -0400 10/11/07, FS wrote: >Hello guys/gals, > >I have a need to track changes to a file being made in real-time. So the >entries in this file are MAC addresses of clients that can get >added/deleted, sometimes multiple entries per second. What I want to do is >to see all the changes were from time A to time B. > >I thought about tail -f, but that only lists the entries being added. >Doing diff would require copying the file and running diff against it >every second or so, and then again it wouldn't necessarily list all the >changes, just the one between the last changed file and the current one. Copy the file, compare the copy against the previous copy. Note that the file may have changed during the copy, so the copy may contain partial changes. >I hope I'm explaining this clearly, but basically the question is, is >there a utility in Linux/Unix world which can track any changes being made >to a file in real-time and list/track/put-in-a-file those changes being >made? > >Many thanks for any help you can provide. Perhaps inotify can resolve the OP's objection to "running diff against it every second or so", but it is an optimization to apply after the problem is solved. Probably diff'ing is not the correct approach at all, and it would be helpful to know what is writing that file, and whether it can be persuaded to write a log file. -- ____________________________________________________________________ TonyN.:' <mailto:tonynelson@xxxxxxxxxxxxxxxxx> ' <http://www.georgeanelson.com/>
