I didn't test it. You're right, I'm simply mistaken. Here's a better (but awkward) illustration of the problem: :~$ python3 -c 'import sys; import shutil; s

I didn't test it. You're right, I'm simply mistaken. Here's a better (but awkward) illustration of the problem: :~$ python3 -c 'import sys; import shutil; shutil.copy(sys.argv[1], "foobar")' < (echo foo ; sleep 1 ; echo bar) Traceback (most recent call last): File "<string>", line 1, in <module> File "/opt/homebrew/Cellar/python@3.9/3.9.9/Frameworks/Python.framework/Versions/3.9/lib/python3.9/shutil.py", line 427, in copy copyfile(src, dst, follow_symlinks=follow_symlinks) File "/opt/homebrew/Cellar/python@3.9/3.9.9/Frameworks/Python.framework/Versions/3.9/lib/python3.9/shutil.py", line 257, in copyfile raise SpecialFileError("`%s` is a named pipe" % fn) shutil.SpecialFileError: `/dev/fd/11` is a named pipe :~$ python3 -c 'import sys; import shutil; shutil.copy(sys.argv[1], "foobar")' =(echo foo ; sleep 1 ; echo bar) Notice the difference: :~$ echo =(echo foo ; sleep 1; echo bar) /tmp/zshbusU5D :~$ echo <(echo foo ; sleep 1; echo bar) /dev/fd/11 /dev/fd/11 is a named pipe, whereas /tmp/zshbEF1D9 is a plain file. There are situations where named pipes fail, where you actually do need a plain file, and I can't think of a single one offhand. :) "I've run into it in the past" is all I can say. And the above snippet at least gives one specific example of a hypothetical case.