(tar)Updating an Archive

Combining Archives

Adding to an Existing Archive

Basic tar Operations

Updating an Archive
===================

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   The `--update' (`-u') option updates a `tar' archive by comparing
the date of the specified archive members against the date of the file
with the same name.  If the file has been modified more recently than
the archive member, then the archive member is deleted (as with
`--delete') and then the file is added to the archive (as with
`--append' (`-r')).  On media where the `--delete' option cannot be
performed (such as magnetic tapes), the `--update' (`-u') option
similarly fails.

   If no archive members are named (either on the command line or via
`--files-from=FILE-OF-NAMES' (`-T FILE-OF-NAMES')), then the entire
archive is processed in this manner.