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    One named pipe is sufficient: prog1 < fifo | prog2 > fifo. Commented Nov 2, 2012 at 16:47
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    @AndreyVihrov that's true, you can substitute an anonymous pipe for one of the named ones. But I like the symmetry :-P Commented Nov 2, 2012 at 17:26
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    @user14284: On Linux, you can probably do it with something like prog1 < fifo | tee /dev/stderr | prog2 | tee /dev/stderr > fifo. Commented Nov 6, 2012 at 10:28
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    If you make it prog2 < fifo0 > fifo1, you can avoid your little dance with exec 30< ... (which by the way only works with bash or yash for fds over 10 like that). Commented Apr 5, 2014 at 20:08
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    @Joost Hmmm, appears you're correct that there is no need, at least in bash. I was probably worried that since the shell performs the redirects (including opening the pipes), it might block—but at least bash forks before opening the fifos. dash seems OK too (but behaves a little differently) Commented Nov 9, 2016 at 17:27