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Choosing and Naming Archive Files
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   By default, `tar' uses an archive file name that was compiled when
it was built on the system; usually this name refers to some physical
tape drive on the machine.  However, the person who installed `tar' on
the system may not set the default to a meaningful value as far as most
users are concerned.  As a result, you will usually want to tell `tar'
where to find (or create) the archive.  The `--file=ARCHIVE-NAME' (`-f
ARCHIVE-NAME') option allows you to either specify or name a file to
use as the archive instead of the default archive file location.

`--file=ARCHIVE-NAME'
`-f ARCHIVE-NAME'
     Name the archive to create or operate on.  Use in conjunction with
     any operation.

   For example, in this `tar' command,

     $ tar -cvf collection.tar blues folk jazz

`collection.tar' is the name of the archive.  It must directly follow
the `-f' option, since whatever directly follows `-f' _will_ end up
naming the archive.  If you neglect to specify an archive name, you may
end up overwriting a file in the working directory with the archive you
create since `tar' will use this file's name for the archive name.

   An archive can be saved as a file in the file system, sent through a
pipe or over a network, or written to an I/O device such as a tape,
floppy disk, or CD write drive.

   If you do not name the archive, `tar' uses the value of the
environment variable `TAPE' as the file name for the archive.  If that
is not available, `tar' uses a default, compiled-in archive name,
usually that for tape unit zero (ie. `/dev/tu00').  `tar' always needs
an archive name.

   If you use `-' as an ARCHIVE-NAME, `tar' reads the archive from
standard input (when listing or extracting files), or writes it to
standard output (when creating an archive).  If you use `-' as an
ARCHIVE-NAME when modifying an archive, `tar' reads the original
archive from its standard input and writes the entire new archive to
its standard output.

     $ cd sourcedir; tar -cf - . | (cd targetdir; tar -xf -)

   To specify an archive file on a device attached to a remote machine,
use the following:

     --file=HOSTNAME:/DEV/FILE NAME

`tar' will complete the remote connection, if possible, and prompt you
for a username and password.  If you use `--file=@HOSTNAME:/DEV/FILE
NAME', `tar' will complete the remote connection, if possible, using
your username as the username on the remote machine.

   If the archive file name includes a colon (`:'), then it is assumed
to be a file on another machine.  If the archive file is
`USER@HOST:FILE', then FILE is used on the host HOST.  The remote host
is accessed using the `rsh' program, with a username of USER.  If the
username is omitted (along with the `@' sign), then your user name will
be used.  (This is the normal `rsh' behavior.)  It is necessary for the
remote machine, in addition to permitting your `rsh' access, to have
the `/usr/ucb/rmt' program installed.  If you need to use a file whose
name includes a colon, then the remote tape drive behavior can be
inhibited by using the `--force-local' option.

   When the archive is being created to `/dev/null', GNU `tar' tries to
minimize input and output operations.  The Amanda backup system, when
used with GNU `tar', has an initial sizing pass which uses this feature.