更新 'shell/shell变量提取赋值.md'

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iProbe 2023-08-12 16:15:50 +08:00
parent 7317fb3f38
commit 27ca5e9a7b

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|-|-|
|表达式|含义| |表达式|含义|
|-|-|
|${var:-aa}|若var为空或未设定, 返回aa, var值不变| |${var:-aa}|若var为空或未设定, 返回aa, var值不变|
|${var:=aa}|若var为空或未设定, 返回aa, var=aa| |${var:=aa}|若var为空或未设定, 返回aa, var=aa|
|${var:+aa}|若var有值 返回aa, var值不变| |${var:+aa}|若var有值 返回aa, var值不变|