处理PowerShell中的404错误

Question

我有一个巨大的博客网址列表，我需要检查其有效性。我从this answer和here那里敲了一个剧本。

这是我的脚本：

$siteURL = 'http://example.com/'
$File    = '.\urls.txt'

$NewContent = Get-Content -Path $File | ForEach-Object {
    $_

    $HTTP_Request  = [System.Net.WebRequest]::Create($siteURL + $_)
    $HTTP_Response = $HTTP_Request.GetResponse()
    $HTTP_Status   = [int]$HTTP_Response.StatusCode

    if ($HTTP_Status -eq 200) {
       " - 200"
    } else {
        " - " + $HTTP_Status
    }

    $HTTP_Response.Close()
}

$NewContent | Out-File -FilePath $File -Encoding Default -Force

我的问题是，当它出现404错误时，它不会将其添加到文件中并在控制台中返回以下错误：

Exception calling "GetResponse" with "0" argument(s): "The remote server
returned an error: (404) Not Found."
At C:\Users\user.name\urlcheck.ps1:19 char:9
+         $HTTP_Response = $HTTP_Request.GetResponse()
+         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : WebException

为什么我收到此错误？

奖金问题：我的“200 - OK”回复正在添加到新的一行，为什么？

Answer 1

为了处理404响应（以及类似的错误响应），我们需要一些错误处理代码：

ForEach-Object {
    $_

    $HTTP_Request = [System.Net.WebRequest]::Create($siteURL + $_)

    try {
        $HTTP_Response = $HTTP_Request.GetResponse()
    }
    catch [System.Net.WebException] {
        # HTTP error, grab response from exception
        $HTTP_Response = $_.Exception.Response
    }
    catch {
        # Something else went horribly wrong, maybe abort?
    }

    $HTTP_Status = [int]$HTTP_Response.StatusCode

    If ($HTTP_Status -eq 200) {
       " - 200"
    }
    Else {
        " - " + $HTTP_Status
    }

    $HTTP_Response.Close()
}

---

奖金问题：我的200 -OK响应会被添加到新行中，为什么？

那是因为你在两个单独的陈述中输出$_和" - " + ...。从顶部删除$_并将其全部合并为一个字符串：

ForEach-Object {
    $HTTP_Request = [System.Net.WebRequest]::Create($siteURL + $_)

    try {
        $HTTP_Response = $HTTP_Request.GetResponse()
    }
    catch [System.Net.WebException] {
        # HTTP error, grab response from exception
        $HTTP_Response = $_.Exception.Response
    }
    catch {
        # Something else went horribly wrong, maybe abort?
    }
    finally {
        # Grab status code and dispose of response stream
        $HTTP_Status = [int]$HTTP_Response.StatusCode
        $HTTP_Response.Dispose()
    }

    "$_ - $HTTP_Status"
}

Answer 2

.NET实现在这一点上设计得有点糟糕。 WebRequest不幸抛出错误状态代码。

基于this答案，您可以使用以下解决方法：

$siteURL = 'http://example.com/'
$file    = '.\urls.txt'

(Get-Content $file) | foreach {
    $HTTP_Response = $null
    try {
        $HTTP_Request = [System.Net.WebRequest]::Create($siteURL + $_)
        $HTTP_Response = $HTTP_Request.GetResponse()
    }
    catch [System.Net.WebException] {
        # catch this specific exception and get the response from it
        $HTTP_Response = $_.Exception.Response
    }
    catch {
        # for other errors, output the error message:
        "{0} - ERROR: {1}" -f $_, $_.Exception.Message
        continue
    }
    finally {
        # standard handling of IDisposable
        if ($HTTP_Response) { $HTTP_Response.Dispose() }
    }
    $HTTP_Status = $HTTP_Response.StatusCode 

    # NOTE: This will also fix your "newline" problem
    "{0} - {1} ({2})" -f $_, [int]$HTTP_Status, $HTTP_Status
} | Out-File $file -Force