如何忽略警告错误? [英] How to ignore warning errors?

问题描述

我有以下 PowerShell 脚本.它选取给定 IP 地址内计算机的 NetBIOS 名称.我正在使用管道将结果转储到文本文件中.问题是，如果 IP 地址不可用，则会打印警告.

I have the following PowerShell script. It picks up the NetBIOS name of computers within a given IP address. I'm using a pipe so as to dump the results into a text file. The problem is that if an IP address is not available, a warning is printed.

这是 PowerShell 脚本:

This is the PowerShell script:

function Get-ComputerNameByIP {
param( $IPAddress = $null )
BEGIN {
    $prefBackup = $WarningPreference
    $WarningPreference = 'SilentlyContinue'
}
PROCESS {
    if ($IPAddress -and $_) {
        throw ‘Please use either pipeline or input parameter’
        break
    } elseif ($IPAddress) {
        ([System.Net.Dns]::GetHostbyAddress($IPAddress))
    } 
    } else {
        $IPAddress = Read-Host "Please supply the IP Address"
        [System.Net.Dns]::GetHostbyAddress($IPAddress)
    }
}
END {
    $WarningPreference = $prefBackup
}

这是我希望忽略的错误消息:

This is the error message I wish to ignore:

警告:请求的名称有效，但未找到请求类型的数据

WARNING: The requested name is valid, but no data of the requested type was found

推荐答案

您想抑制警告，而不是错误.警告可以通过设置 $WarningPreference 变量到 SilentlyContinue:

You want to suppress warnings, not errors. Warnings can be silenced completely by setting the $WarningPreference variable to SilentlyContinue:

PS C:\> Write-Warning 'foo'
WARNING: foo
PS C:\> $prefBackup = $WarningPreference
PS C:\> $WarningPreference = 'SilentlyContinue'
PS C:\> Write-Warning 'foo'
PS C:\> $WarningPreference = $prefBackup
PS C:\> Write-Warning 'foo'
WARNING: foo

该设置与当前范围有关，因此如果您想取消函数的所有警告，只需在函数的开头设置首选项:

The setting pertains to the current scope, so if you want to suppress all warnings for your function you'd simply set the preference at the beginning of your function:

function Get-ComputerNameByIP {
    param( $IPAddress = $null )

    BEGIN {
        $WarningPreference = 'SilentlyContinue'
    }

    PROCESS {
        if ($IPAddress -and $_) {
            throw ‘Please use either pipeline or input parameter’
            break
        } elseif ($IPAddress) {
            [System.Net.Dns]::GetHostbyAddress($IPAddress)
        } 
            [System.Net.Dns]::GetHostbyAddress($_)
        } else {
            $IPAddress = Read-Host "Please supply the IP Address"
            [System.Net.Dns]::GetHostbyAddress($IPAddress)
        }
    }

    END {}
}

如果您只想针对特定语句抑制警告，更简单的方法是重定向警告输出流到$null:

If you want warnings suppressed for specific statements only, a simpler way is to redirect the warning output stream to $null:

[System.Net.Dns]::GetHostbyAddress($IPAddress) 3>$null

警告流重定向仅在 PowerShell v3 及更新版本中可用.

Warning stream redirection is only available in PowerShell v3 and newer, though.

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