1	#!/bin/bash
2
3	### $PWD
4	# Just test that it has a slash for now.
5	echo $PWD | grep -o /
6	# status: 0
7
8	### $?
9	echo $? # starts out as 0
10	sh -c 'exit 33'
11	echo $?
12	# stdout-json: "0\n33\n"
13	# status: 0
14
15	### $#
16	set -- 1 2 3 4
17	echo $#
18	# stdout: 4
19	# status: 0
20
21	### $-
22	# dash's behavior seems most sensible here?
23	$SH -o nounset -c 'echo $-'
24	# OK bash stdout: huBc
25	# OK dash stdout: u
26	# OK mksh stdout: uhc
27	# status: 0
28
29	### $_
30	# This is bash-specific.
31	echo hi
32	echo $_
33	# stdout-json: "hi\nhi\n"
34	# N-I dash/mksh stdout-json: "hi\n\n"
35
36	### $$ looks like a PID
37	# Just test that it has decimal digits
38	echo $$ | egrep '[0-9]+'
39	# status: 0
40
41	### $$ doesn't change with subshell
42	# Just test that it has decimal digits
43	set -o errexit
44	die() {
45	echo 1>&2 "$@"; exit 1
46	}
47	parent=$$
48	test -n "$parent" || die "empty PID in parent"
49	( child=$$
50	test -n "$child" || die "empty PID in child"
51	test "$parent" = "$child" || die "should be equal: $parent != $child"
52	)
53	exit 3 # make sure we got here
54	# stdout-json: ""
55	# status: 3
56
57	### $BASHPID DOES change with subshell
58	set -o errexit
59	die() {
60	echo 1>&2 "$@"; exit 1
61	}
62	parent=$BASHPID
63	test -n "$parent" || die "empty BASHPID in parent"
64	( child=$BASHPID
65	test -n "$child" || die "empty BASHPID in child"
66	test "$parent" != "$child" || die "should not be equal: $parent = $child"
67	)
68	exit 3 # make sure we got here
69	# stdout-json: ""
70	# status: 3
71	# N-I dash status: 1
72
73	### Background PID $! looks like a PID
74	sleep 0.01 &
75	pid=$!
76	wait
77	echo $pid | egrep '[0-9]+' >/dev/null
78	echo status=$?
79	# stdout: status=0
80
81	### $PPID
82	echo $PPID | egrep '[0-9]+'
83	# status: 0
84
85	# NOTE: There is also $BASHPID
86
87	### $PIPESTATUS
88	echo hi | sh -c 'cat; exit 33' | wc -l >/dev/null
89	argv.py "${PIPESTATUS[@]}"
90	# status: 0
91	# stdout: ['0', '33', '0']
92	# N-I dash stdout-json: ""
93	# N-I dash status: 2
94
95	### $RANDOM
96	expr $0 : '.*/osh$' && exit 99 # Disabled because of spec-runner.sh issue
97	echo $RANDOM | egrep '[0-9]+'
98	# status: 0
99	# N-I dash status: 1