Jon LaBadie wrote:

The mtime + the inode number are compared by gnutar.

Paul,
I haven't looked at the code, but wouldn't it use ctime rather than mtime?
If a file has had its permissions or ownership changed that file should
also be a candidate for backing up so that restoration is accurate.

Yes you're right (but I'm too, a little):

Having a closer look in the code

   File "incremen.c"

   395    if (0 < getline (&buf, &bufsize, fp))
   ...  (read the first line from the file, error checking etc)
   400        unsigned long u = (errno = 0, strtoul (buf, &ebuf, 10));
   ...  (convert to long int, and some more error checking)
   409          newer_mtime_option = t;
         OK, now the "newer_mtime_option" is initialized from the
         integer on the first line in the file.

  Then:
   299        else
   300          if (children == CHANGED_CHILDREN
   301              && stat_data.st_mtime < newer_mtime_option
   302              && (!after_date_option
   303                  || stat_data.st_ctime < newer_ctime_option))
   304            add_to_accumulator (accumulator, "N", 1);
   305          else
   306            add_to_accumulator (accumulator, "Y", 1);

And indeed it is compared to mtime!!!
I could not find the point where newer_ctime_option was initialised.

BUT, a closer look after receiving your mail revealed:

in common.h:

    #define newer_ctime_option newer_mtime_option

So gnutar compares both ctime and mtime of each file to the same
timestamp.


--
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
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