PowerShell：函数插值

发布于 2024-10-16 18:43:57 字数 400 浏览 1 评论 0原文

我是 PowerShell 初学者。应该使用 $() 让 Write-Host 来评估此函数的原因是什么？

我从文档中找不到原因。

PS C:\Temp> Write-Host [math]::round($diff.TotalMinutes, 2)
[math]::round 751681,102679735 2

___________________________________________________________________________________________________________

PS C:\Temp> Write-Host $([math]::round($diff.TotalMinutes, 2))
751681,1

原文

I'm a PowerShell beginner. What is the reason that one should use $() to get Write-Host to evaluate this function?

I could not find a reason for this from the documentation.

PS C:\Temp> Write-Host [math]::round($diff.TotalMinutes, 2)
[math]::round 751681,102679735 2

___________________________________________________________________________________________________________

PS C:\Temp> Write-Host $([math]::round($diff.TotalMinutes, 2))
751681,1

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箜明 2024-10-23 18:43:57

您可以删除美元符号并仅使用

Write-Host ([math]::round($diff.TotalMinutes, 2))

解析器需要的括号，以便首先计算表达式，然后将其绑定到参数-Object。
当解析器期望字符串将是表达式以及何时将其视为字符串并将其传递给命令而不进行评估时，有一些规则。更多信息请参阅PowerShell 实战。

如果有多个表达式，则需要美元符号，以 ; 分隔

Write-Host $(get-date; 1; "test")

You can remove the dollar sign and use just

Write-Host ([math]::round($diff.TotalMinutes, 2))

The brackets are needed for the parser so that first the expression is evaluated and then bound to parameter -Object.
There are some rules when parser expects that the string will be expression and when it treats it as a string and passes it to the command without evaluating. More info can be found in PowerShell in Action.

Dollar sign is needed if there are more expressions separated by ;