1	#!/usr/bin/env bash
2	#
3	# POSIX rule about special builtins pointed at:
4	#
5	# https://www.reddit.com/r/oilshell/comments/5ykpi3/oildev_is_alive/
6
7	#### : is special and prefix assignments persist after special builtins
8	# Bash only implements it behind the posix option
9	#test -n "$BASH_VERSION" && set -o posix
10	case $SH in
11	*dash|*zsh|*osh)
12	;;
13	*)
14	set -o posix
15	;;
16	esac
17	foo=bar :
18	echo -$foo-
19	## STDOUT:
20	-bar-
21	## END
22	## BUG zsh STDOUT:
23	--
24	## END
25
26	#### true is not special
27	foo=bar true
28	echo $foo
29	## stdout:
30
31	#### Shift is special and the whole script exits if it returns non-zero
32	test -n "$BASH_VERSION" && set -o posix
33	set -- a b
34	shift 3
35	echo status=$?
36	## stdout-json: ""
37	## status: 1
38	## OK dash status: 2
39	## BUG bash/zsh status: 0
40	## BUG bash/zsh STDOUT:
41	status=1
42	## END
43
44	#### set is special and fails, even if using || true
45	shopt -s invalid_ || true
46	echo ok
47	set -o invalid_ || true
48	echo should not get here
49	## STDOUT:
50	ok
51	## END
52	## status: 1
53	## OK dash status: 2
54	## BUG bash status: 0
55	## BUG bash STDOUT:
56	ok
57	should not get here
58	## END
59
60	#### Special builtins can't be redefined as functions
61	# bash manual says they are 'found before' functions.
62	test -n "$BASH_VERSION" && set -o posix
63	export() {
64	echo 'export func'
65	}
66	export hi
67	echo status=$?
68	## status: 2
69	## BUG mksh/zsh status: 0
70	## BUG mksh/zsh stdout: status=0
71
72	#### Non-special builtins CAN be redefined as functions
73	test -n "$BASH_VERSION" && set -o posix
74	true() {
75	echo 'true func'
76	}
77	true hi
78	echo status=$?
79	## STDOUT:
80	true func
81	status=0
82	## END