1	#!/usr/bin/env bash
2
3	#### Process sub input
4	f=_tmp/process-sub.txt
5	{ echo 1; echo 2; echo 3; } > $f
6	cat <(head -n 2 $f) <(tail -n 2 $f)
7	## STDOUT:
8	1
9	2
10	2
11	3
12	## END
13
14	#### Process sub output
15	{ echo 1; echo 2; echo 3; } > >(tac)
16	## STDOUT:
17	3
18	2
19	1
20	## END
21
22	#### Non-linear pipeline with >()
23	stdout_stderr() {
24	echo o1
25	echo o2
26
27	sleep 0.1 # Does not change order
28
29	{ echo e1;
30	echo warning: e2
31	echo e3;
32	} >& 2
33	}
34	stdout_stderr 2> >(grep warning) | tac >$TMP/out.txt
35	wait $! # this does nothing in bash 4.3, but probably does in bash 4.4.
36	echo OUT
37	cat $TMP/out.txt
38	# PROBLEM -- OUT comes first, and then 'warning: e2', and then 'o2 o1'. It
39	# looks like it's because nobody waits for the proc sub.
40	# http://lists.gnu.org/archive/html/help-bash/2017-06/msg00018.html
41	## STDOUT:
42	OUT
43	warning: e2
44	o2
45	o1
46	## END
47
48	#### $(<file) idiom with process sub
49	echo FOO >foo
50
51	# works in bash and zsh
52	echo $(<foo)
53
54	# this works in zsh, but not in bash
55	tr A-Z a-z < <(<foo)
56
57	cat < <(<foo; echo hi)
58
59	## STDOUT:
60	FOO
61	hi
62	## END
63	## OK zsh STDOUT:
64	FOO
65	foo
66	FOO
67	hi
68	## END