1	#!/usr/bin/env bash
2	#
3	# NOTE:
4	# - $! is tested in background.test.sh
5	# - $- is tested in sh-options
6	#
7	# TODO: It would be nice to make a table, like:
8	#
9	# $$ $BASHPID $PPID $SHLVL $BASH_SUBSHELL
10	# X
11	# (Subshell, Command Sub, Pipeline, Spawn $0)
12	#
13	# And see whether the variable changed.
14
15	#### $PWD is set
16	# Just test that it has a slash for now.
17	echo $PWD | grep /
18	## status: 0
19
20	#### $PWD is not only set, but exported
21	env | grep PWD
22	## status: 0
23	## BUG mksh status: 1
24
25	#### $HOME is NOT set
26	home=$(echo $HOME)
27	test "$home" = ""
28	echo status=$?
29
30	env | grep HOME
31	echo status=$?
32
33	# not in interactive shell either
34	$SH -i -c 'echo $HOME' | grep /
35	echo status=$?
36
37	## STDOUT:
38	status=0
39	status=1
40	status=1
41	## END
42
43
44	#### $1 .. $9 are scoped, while $0 is not
45	func() { echo $0 $1 $2 | sed -e 's/.*sh/sh/'; }
46	func a b
47	## stdout: sh a b
48
49	#### $?
50	echo $? # starts out as 0
51	sh -c 'exit 33'
52	echo $?
53	## stdout-json: "0\n33\n"
54	## status: 0
55
56	#### $#
57	set -- 1 2 3 4
58	echo $#
59	## stdout: 4
60	## status: 0
61
62	#### $_
63	# This is bash-specific.
64	echo hi
65	echo $_
66	## stdout-json: "hi\nhi\n"
67	## N-I dash/mksh stdout-json: "hi\n\n"
68
69	#### $$ looks like a PID
70	# Just test that it has decimal digits
71	echo $$ | egrep '[0-9]+'
72	## status: 0
73
74	#### $$ doesn't change with subshell or command sub
75	# Just test that it has decimal digits
76	set -o errexit
77	die() {
78	echo 1>&2 "$@"; exit 1
79	}
80	parent=$$
81	test -n "$parent" || die "empty PID in parent"
82	( child=$$
83	test -n "$child" || die "empty PID in subshell"
84	test "$parent" = "$child" || die "should be equal: $parent != $child"
85	echo 'subshell OK'
86	)
87	echo $( child=$$
88	test -n "$child" || die "empty PID in command sub"
89	test "$parent" = "$child" || die "should be equal: $parent != $child"
90	echo 'command sub OK'
91	)
92	exit 3 # make sure we got here
93	## status: 3
94	## STDOUT:
95	subshell OK
96	command sub OK
97	## END
98
99	#### $BASHPID DOES change with subshell and command sub
100	set -o errexit
101	die() {
102	echo 1>&2 "$@"; exit 1
103	}
104	parent=$BASHPID
105	test -n "$parent" || die "empty BASHPID in parent"
106	( child=$BASHPID
107	test -n "$child" || die "empty BASHPID in subshell"
108	test "$parent" != "$child" || die "should not be equal: $parent = $child"
109	echo 'subshell OK'
110	)
111	echo $( child=$BASHPID
112	test -n "$child" || die "empty BASHPID in command sub"
113	test "$parent" != "$child" ||
114	die "should not be equal: $parent = $child"
115	echo 'command sub OK'
116	)
117	exit 3 # make sure we got here
118	## status: 3
119	## STDOUT:
120	subshell OK
121	command sub OK
122	## END
123	## N-I dash status: 1
124	## N-I dash stdout-json: ""
125
126	#### Background PID $! looks like a PID
127	sleep 0.01 &
128	pid=$!
129	wait
130	echo $pid | egrep '[0-9]+' >/dev/null
131	echo status=$?
132	## stdout: status=0
133
134	#### $PPID
135	echo $PPID | egrep '[0-9]+'
136	## status: 0
137
138	# NOTE: There is also $BASHPID
139
140	#### $PIPESTATUS
141	echo hi | sh -c 'cat; exit 33' | wc -l >/dev/null
142	argv.py "${PIPESTATUS[@]}"
143	## status: 0
144	## stdout: ['0', '33', '0']
145	## N-I dash stdout-json: ""
146	## N-I dash status: 2
147
148	#### $RANDOM
149	expr $0 : '.*/osh$' && exit 99 # Disabled because of spec-runner.sh issue
150	echo $RANDOM | egrep '[0-9]+'
151	## status: 0
152	## N-I dash status: 1
153
154	#### $UID and $EUID
155	# These are both bash-specific.
156	set -o errexit
157	echo $UID | egrep -o '[0-9]+' >/dev/null
158	echo $EUID | egrep -o '[0-9]+' >/dev/null
159	echo status=$?
160	## stdout: status=0
161	## N-I dash/mksh stdout-json: ""
162	## N-I dash/mksh status: 1
163
164	#### $OSTYPE is non-empty
165	test -n "$OSTYPE"
166	echo status=$?
167	## STDOUT:
168	status=0
169	## END
170	## N-I dash/mksh STDOUT:
171	status=1
172	## END
173
174	#### $HOSTNAME
175	test "$HOSTNAME" = "$(hostname)"
176	echo status=$?
177	## STDOUT:
178	status=0
179	## END
180	## N-I dash/mksh STDOUT:
181	status=1
182	## END
183