出于某种原因,如果我的XML文件只包含一个计算机节点,但它返回一个列表(这是我总是期望的),如果有的话,下面的Read-TestControllerXml powershell函数返回一个System.Xml.XmlElement类型的对象多个计算机节点。为什么这个Powershell函数有时会返回一个列表,而其他时间会返回一个XmlElement?
的XML文件的示例如下:
<test_controller>
<defaults>
<nunit path='C:\Program Files (x86)\NUnit 2.6.2\bin\nunit-console.exe' />
<nunit_results local_path='C:\Test_Results' remote_path='C:\Test_Results' />
<powershell path='C:\windows\system32\WindowsPowerShell\v1.0\powershell.exe' />
<psexec path='C:\PSTools\PsExec.exe' />
</defaults>
<platform os='windows' version='2012' cpu='x64'>
<computer hostname='VM-2012R2-03' alias='standalone-01' configuration='standalone' image='VM-2012R2-03:Clean' />
</platform>
</test_controller>
这里是PowerShell的功能:
####################################################################
# Parses the TestController.xml file and returns a list of Computer XML objects.
#
# Syntax:
# Read-TestControllerXml [-TestControllerXml] <path to TestController.xml> [<CommonParameters>]
#
# Returns: An array of [Xml] nodes for each of the <computer> tags in TestController.xml.
####################################################################
function Read-TestControllerXml
{
[CmdletBinding()]
Param
(
[parameter(Mandatory=$true)]
[string] $TestControllerXml
)
$ErrorActionPreference = "Stop"
# Read the TestController XML configuration file
$TestController = [xml] (Get-Content $TestControllerXml)
Write-Verbose "Selecting computer nodes..."
$computerNodes = $TestController.SelectNodes("//test_controller/platform/computer")
Write-Verbose "Selecting default nodes..."
$defaultNodes = $TestController.SelectSingleNode("//test_controller/defaults")
$computers = @()
foreach ($computerNode in $computerNodes)
{
Write-Verbose "***** Before adding default attributes *****"
Write-Verbose "$($computerNode.OuterXml)"
# Add default attributes to the node
foreach ($dnode in $defaultNodes.ChildNodes)
{
if ($dnode.NodeType -eq "Comment") { continue } # Skip comments.
# Search for the node items in the defaults section
$cnode = $computerNode
if ($dnode.Name -ne $computerNode.Name)
{
Write-Verbose "Selecting '$($dnode.Name)' nodes..."
$cnode = $computerNode.SelectSingleNode($dnode.Name)
}
# Append the default nodes that do not exist in the computer specific sections
if ($cnode -eq $null)
{
Write-Verbose "*** cnode != null cnode.OuterXml is: '$($cnode.OuterXml)'"
Write-Verbose "Appending default '$($dnode.Name)' node that don't exist in the computer nodes..."
$cnode=$computerNode.AppendChild($TestController.ImportNode($dnode, $true))
}
# Append the default attributes that do not exist in the computer specific sections
else
{
Write-Verbose "Appending default attributes that don't exist in computer nodes..."
foreach ($attribute in $dnode.Attributes)
{
if (-not $cnode.HasAttribute($attribute.Name))
{
Write-Verbose "Adding attribute '$($attribute.Name)=$($attribute.Value)' to the computer node."
$cnode.SetAttribute($attribute.Name, $attribute.Value)
}
}
}
}
Write-Verbose "***** After adding default attributes *****"
Write-Verbose "$($computerNode.OuterXml)"
Write-Verbose "************************************************************"
$computers += $computerNode
}
return $computers
}
有没有理由讨厌powershell。它试图用一个元素来帮助你。你的数据总是好的! – Matt 2014-09-19 23:25:49
您必须记住,PowerShell是一种'Shell脚本语言',主要针对系统管理员。管理员不必担心它们的函数是否返回0,1或N结果,以便它在管道中工作。也就是说,当一个标量值放在管道的前端时,管道预计会处理该单个对象。当代表一个集合的值被放在一个管道的前端时,管道预期会处理集合中的每个单独对象而不是集合作为单个对象。 – 2014-09-20 04:03:41
逗号技巧只是将数组包装到另一个数组中,以便通过展开数组输出的单个对象是原始数组。注意:一般来说这不建议用于正确的流水线操作,例如如果我想使用你的修改函数,我不得不这样做'Read-TestControllerXml $ xmlPath | Foreach {$ _} | Foreach {..用XmlElement做一些事情......}'而不是像这样直接做'Read-TestControllerXml $ xmlPath | Foreach {..用XmlElement做一些事情..} – 2014-09-20 04:07:13