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(tar.info)concatenate

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Combining Archives with `--concatenate'
---------------------------------------

   Sometimes it may be convenient to add a second archive onto the end
of an archive rather than adding individual files to the archive.  To
add one or more archives to the end of another archive, you should use
the `--concatenate' (`--catenate', `-A') operation.

   To use `--concatenate', name the archives to be concatenated on the
command line.  (Nothing happens if you don't list any.)  The members,
and their member names, will be copied verbatim from those archives.  If
this causes multiple members to have the same name, it does not delete
any members; all the members with the same name coexist.

   To demonstrate how `--concatenate' works, create two small archives
called `bluesrock.tar' and `folkjazz.tar', using the relevant files
from `practice':

     $ tar -cvf bluesrock.tar blues rock
     blues
     classical
     $ tar -cvf folkjazz.tar folk jazz
     folk
     jazz

If you like, You can run `tar --list' to make sure the archives contain
what they are supposed to:

     $ tar -tvf bluesrock.tar
     -rw-rw-rw- melissa user    105 1997-01-21 19:42 blues
     -rw-rw-rw- melissa user     33 1997-01-20 15:34 rock
     $ tar -tvf folkjazz.tar
     -rw-rw-rw- melissa user     20 1996-09-23 16:44 folk
     -rw-rw-rw- melissa user     65 1997-01-30 14:15 jazz

   We can concatenate these two archives with `tar':

     $ cd ..
     $ tar --concatenate --file=bluesrock.tar jazzfolk.tar

   If you now list the contents of the `bluesclass.tar', you will see
that now it also contains the archive members of `jazzfolk.tar':

     $ tar --list --file=bluesrock.tar
     blues
     rock
     jazz
     folk

   When you use `--concatenate', the source and target archives must
already exist and must have been created using compatible format
parameters.  The new, concatenated archive will be called by the same
name as the first archive listed on the command line.

   Like `--append' (`-r'), this operation cannot be performed on some
tape drives, due to deficiencies in the formats those tape drives use.

   It may seem more intuitive to you to want or try to use `cat' to
concatenate two archives instead of using the `--concatenate'
operation; after all, `cat' is the utility for combining files.

   However, `tar' archives incorporate an end-of-file marker which must
be removed if the concatenated archives are to be read properly as one
archive.  `--concatenate' removes the end-of-archive marker from the
target archive before each new archive is appended.  If you use `cat'
to combine the archives, the result will not be a valid `tar' format
archive.  If you need to retrieve files from an archive that was added
to using the `cat' utility, use the `--ignore-zeros' (`-i') option.
Note: Ignore Zeros, for further information on dealing with archives
improperly combined using the `cat' shell utility.

   You must specify the source archives using `--file=ARCHIVE-NAME'
(`-f ARCHIVE-NAME') (Note: file).  If you do not specify the target
archive, `tar' uses the value of the environment variable `TAPE', or,
if this has not been set, the default archive name.