Compares archive members with their counterparts in the file
system, and reports differences in file size, mode, owner,
modification date and contents. See compare.
--concatenate
-A
Appends other tar archives to the end of the archive.
See concatenate.
Adds files to the end of the archive,
but only if they are newer than their counterparts already in the
archive, or if they do not already exist in the archive.
See update.
Published under the terms of the GNU General Public License