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Normally I use tar with either tar -cvzf to create or to tar -xvzf to extract. Both cases need -f to specify the file. I know sometimes I will supply -f from standard input or standard output, but I still need -f switch.

So is there any situation I do not specify -f ?

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  • Will this work for you: tar xz < file ? – andrew.46 Feb 28 '19 at 6:16
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You do not need -f when you use stdin/stdout.

You may for instance do tar -cv foo > foo.tar, which will create foo.tar.

This may also be used to pipe together commands. Say you want to create a 7z compressed tar file:

tar -cv foo/ | 7z a -si foo.tar.7z

or you can do remote backups easily

tar -cv foo/ | ssh user@example.org "cat > backup.tar"

The same may also be applied in reverse

ssh user@example.org "cat backup.tar" | tar -xv 

to extract the tar ball.

So yes, there's cases when you don't need or don't want the f switch.

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You can hardcode the archive file

  $ export TAPE=archive-file

This is possible but not recommended

See manual

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