bash Default values düzenlemesi

LittleGreenCat bu gisti düzenledi 1744770144. Düzenlemeye git

1 file changed, 62 insertions

bash.md(dosya oluşturuldu)

		@@ -0,0 +1,62 @@
1	+	Частенько требуется в bash скрипте указать значение переменной по умолчанию, например если не задано прямо.. Однако не все так просто...
2	+	Краткий списочек с описанием логики.
3	+
4	+	```bash
5	+	# bash one liner
6	+	# --------------
7	+
8	+	x="foo" && echo "${x:-bar} (x = $x)"
9	+	# foo (x = foo)
10	+
11	+	x="" && echo "${x:-bar} (x = $x)"
12	+	# bar (x = )
13	+
14	+	unset x && echo "${x:-bar} (x = $x)"
15	+	# bar (x = )
16	+
17	+	x="foo" && echo "${x-bar} (x = $x)"
18	+	# foo (x = foo)
19	+
20	+	x="" && echo "${x-bar} (x = $x)"
21	+	# (x = )
22	+
23	+	unset x && echo "${x-bar} (x = $x)"
24	+	# bar (x = )
25	+
26	+	x="foo" && echo "${x:=bar} (x = $x)"
27	+	# foo (x = foo)
28	+
29	+	x="" && echo "${x:=bar} (x = $x)"
30	+	# bar (x = bar)
31	+
32	+	unset x && echo "${x:=bar} (x = $x)"
33	+	# bar (x = bar)
34	+
35	+	x="foo" && echo "${x=bar} (x = $x)"
36	+	# foo (x = foo)
37	+
38	+	x="" && echo "${x=bar} (x = $x)"
39	+	# (x = )
40	+
41	+	unset x && echo "${x=bar} (x = $x)"
42	+	# bar (x = bar)
43	+
44	+	x="foo" && echo "(x = $x)" && echo "${x:?error message}"
45	+	# (x = foo) foo
46	+
47	+	x="" && echo "(x = $x)" && echo "${x:?error message}"
48	+	# (x = ) bash: x: error message
49	+
50	+	unset x && echo "(x = $x)" && echo "${x:?error message}"
51	+	# (x = ) bash: x: error message
52	+
53	+	x="foo" && echo "${x:+bar} (x = $x)"
54	+	# bar (x = foo)
55	+
56	+	x="" && echo "${x:+bar} (x = $x)"
57	+	# (x = )
58	+
59	+	unset x && echo "${x:+bar} (x = $x)"
60	+	# (x = )
61	+	```
62	+	Опубликовано в [gitgate](https://t.me/gitgate)

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