According to the manual and many posts I should be able to do:
biber --output_format=bibtex test.bcf
And I'll get a new .bib file called test_biber.bib containing all cited entries in test.tex, in citation order. But, when I do that, and then I get:
Biber: Output format 'bibtex' is only valid in tool mode
So I added the --tool, but then biber expects a bib file and looks for test.bcf.bib. So it doesn't work. And if I use mybibfile.bib as an argument, then it just rewrites mybibfile_biber.bib with nicer format. So, am I doing something wrong?