4.2.6 Comparing Archive Members with the File System
The --compare (-d), or --diff operation compares
specified archive members against files with the same names, and then
reports differences in file size, mode, owner, modification date and
contents. You should only specify archive member names, not file
names. If you do not name any members, then tar will compare the
entire archive. If a file is represented in the archive but does not
exist in the file system, tar reports a difference.
You have to specify the record size of the archive when modifying an
archive with a non-default record size.
tar ignores files in the file system that do not have
corresponding members in the archive.
The following example compares the archive members rock,
blues and funk in the archive bluesrock.tar with
files of the same name in the file system. (Note that there is no file,
funk; tar will report an error message.)
$ tar --compare --file=bluesrock.tar rock blues funk
tar: funk not found in archive
The spirit behind the --compare (--diff, -d) option is to check whether the
archive represents the current state of files on disk, more than validating
the integrity of the archive media. For this later goal, See verify.
Published under the terms of the GNU General Public License