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	foo=bar :
11	echo $foo
12	# stdout: bar
13
14	### true is not special
15	foo=bar true
16	echo $foo
17	# stdout:
18
19	### Shift is special and the whole script exits if it returns non-zero
20	test -n "$BASH_VERSION" && set -o posix
21	set -- a b
22	shift 3
23	echo status=$?
24	# stdout-json: ""
25	# status: 1
26	# OK dash status: 2
27	# BUG bash status: 0
28	# BUG bash stdout-json: "status=1\n"
29
30	### Special builtins can't be redefined as functions
31	# bash manual says they are 'found before' functions.
32	test -n "$BASH_VERSION" && set -o posix
33	export() {
34	echo 'export func'
35	}
36	export hi
37	echo status=$?
38	# status: 2
39	# BUG mksh status: 0
40	# BUG mksh stdout: status=0
41
42	### Non-special builtins CAN be redefined as functions
43	test -n "$BASH_VERSION" && set -o posix
44	true() {
45	echo 'true func'
46	}
47	true hi
48	echo status=$?
49	# stdout-json: "true func\nstatus=0\n"