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  • So I understand < <(...) feeds a substituted process's output to a command to the left by writing it to a temporary FIFO and the reading it, all without the overhead of subshelling. Commented Jul 5, 2020 at 21:48
  • Kinda correct but not exactly: /dev/fd/* is not necessarily FIFO itself - it's a file descriptor entry, and pairs of file descriptors are passed between subprocesses in pipelines (which is what <() does underneath the hood, it's really series of pipelines). As for subshelling, I'm not sure where that comes from as bash 4.4 manual that I have says absolutely nothing in the section about process substitution. You may want to revise or research that a bit more maybe. In fact try this: cat < <(echo $BASH_SUBSHELL) Commented Jul 5, 2020 at 22:46
  • It's written FIFO OR /dev/fd/* Commented Jul 5, 2020 at 22:48