Different tar(1) implementations default to different input and output
locations when none is specified. This can include tape devices like
/dev/st0 (on Linux) or /dev/sa0 (on FreeBSD), but may be overridden by
compilation options or environment variables. Using the f option with
the special value of - instructs tar(1) to read from stdin and write to
stdout instead of the default.
Signed-off-by: Samuel Karp <me@samuelkarp.com>
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