In general, it is not possible to know which file has changed by looking at the size of the file or the time stamp.

In general, the command

Code:

cmp

will report the byte at which the first difference is found.

Code:

sum

or (better)

Code:

md5sum

are statistically highly likely to work. Well, the chances of md5sum reporting the same hash value for two different files is vanishingly low, but cmp is probably faster.

So you should begin by determining if the files are indeed different

Code:

cmp file1.tar file2.tar
file1.tar file2.tar differ: differ: char 6, line 1

If they are, you should next compare the table of contents:

Code:

tar tf file1.tar >/tmp/file1.toc
tar tf file2.tar >/tmp/file2.toc
cmp /tmp/file1.toc /tmp/file2.toc

If the TOCs differ, then use sdiff

Code:

sdiff /tmp/file1.toc /tmp/file2.toc

If the TOC does not differ, you will need to extract the files from the two .tar files, one by one, and cmp these extracted files.

Code:

[ ! -d /tmp/file1 ] && mkdir /tmp/file1
[ ! -d /tmp/file2 ] && mkdir /tmp/file2
tar tf file1.tar >/tmp/file1/file1.toc
tar tf file2.tar >/tmp/file2/file2.toc
for f in $(cat /tmp/file1/file1.toc)
do
   cd /tmp/file1
   tar xf /path/to/file1.tar $f
   cd /tmp/file2
   tar xf /path/to/file2.tar $f
   Echo comparing  /tmp/file1/$f  /tmp/file2/$f
   cmp /tmp/file1/$f /tmp/file2/$f
done