How to copy binary data to stdout?

[guettli]

I try to get a files or directories like this:

k node-shell mynode  -- tar -czf- /var/log/... > o.tgz

But this fails, because tar does not write to a tty:

tar: Refusing to write archive contents to terminal (missing -f option?)
tar: Error is not recoverable: exiting now

Is there a way to make node-shell not create a tty?

I tried this workaround:

k node-shell mynode  -- sh -c "tar -czf- /var/log/... |cat" > o.tgz

But this seems to alter the binary data slightly. Extracting it does not work:

gzip: stdin: invalid compressed data--format violated

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It would be really great if output of binary data would be supported.