Why “process substitution” is a late feature in Unix shells(utcc.utoronto.ca)

    The following is included for compatibility with Bird and Wadler (1988).
    The normal Miranda style is to use the curried form `zip2'.

    > zip :: ([*],[**])->[(*,**)]
    > zip (x,y) = zip2 x y

  > echo a b c d | nth 0 3
  a d

  #!/bin/bash

  c=""
  for n in "$@"
  do
    n=$((n+1))
    args="${args}${c}\$$n"
    c=', '
  done
  awk "{ print ${args}; }"

  awk "{ print $(echo "$@" | args math '1+{}' | replace '^' '$' | trim | joinlines ', '); }"

    awp () {
     local a
     a=()
     while [[ -z ${1:#-*} ]]
     do
      a=($a $1)
      shift
     done
     local n
     n=$1
     shift
     awk $a '{print $'$n'}' $*
    }

  :~$ 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/[email protected]/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/[email protected]/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)

  :~$ echo =(echo foo ; sleep 1; echo bar)
  /tmp/zshbusU5D
  :~$ echo <(echo foo ; sleep 1; echo bar)
  /dev/fd/11

  program/
    input/
      x
      y
    output/
      x+y
      x-y

  the_prog > the_file