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