LittleGreenCat zrewidował ten Gist . Przejdź do rewizji
1 file changed, 62 insertions
bash.md(stworzono plik)
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| 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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