PowerShell 技能连载 - 让新手运行 PowerShell 脚本

假设您要把一段 PowerShell 脚本传给一个没有经验的用户。如何确保对方正确地运行了您的脚本呢?由于操作系统和组策略的限制,有可能并没有一个上下文菜单命令来运行 PowerShell 脚本。这个用户也有可能改变了执行策略设置。

不过有一个非常简单的解决方案:将您的脚本和一个快捷方式一起分发。这个快捷方式包含所有必须的命令行开关,可以通过双击快速执行。您甚至可以为快捷方式分配一个漂亮的图标。然而,您需要一些小技巧来实现。典型的快捷方式使用绝对路径,所以当您将文件发送给客户时这个快捷方式可能无法执行,因为您无法知道客户将把这个文件保存到哪里。诀窍是在快捷方式中使用相对路径。

只需要确保调整了第一行指向希望执行的脚本,然后运行这段代码,就可以了。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
# specify the path to your PowerShell script
$ScriptPath = "C:\test\test.ps1"

# create a lnk file
$shortcutPath = [System.IO.Path]::ChangeExtension($ScriptPath, "lnk")
$filename = [System.IO.Path]::GetFileName($ScriptPath)

# create a new shortcut
$shell = New-Object -ComObject WScript.Shell
$scut = $shell.CreateShortcut($shortcutPath)
# launch the script with powershell.exe:
$scut.TargetPath = "powershell.exe"
# skip profile scripts and enable execution policy for this one call
# IMPORTANT: specify only the script file name, not the complete path
$scut.Arguments = "-noprofile -executionpolicy bypass -file ""$filename"""
# IMPORTANT: leave the working directory empty. This way, the
# shortcut uses relative paths
$scut.WorkingDirectory = ""
# optinally specify a nice icon
$scut.IconLocation = "$env:windir\system32\shell32.dll,162"
# save shortcut file
$scut.Save()

# open shortcut file in File Explorer
explorer.exe "/select,$shortcutPath"

这个快捷方式就放在您的 PowerShell 脚本相邻的位置。它使用相对路径,由于我们保证快捷方式和 PowerShell 脚本放在相同的路径,所以它能够完美地工作——这样您可以将两个文件打包,然后将它们发送给客户。当他解压了文件,快捷方式仍然可以工作。您甚至可以将快捷方式改为想要的名字,例如“双击我执行”。

重要:快捷方式使用相对路径来确保这个解决方案便携化。如果您将快捷方式移动到脚本之外的文件夹,那么该快捷方式显然不能工作。。

评论

PowerShell 技能连载 - 修复 PowerShellGet 发布

如果您在使用 Publish-Module 来将您的模块发布到 PowerShell 仓库,并且您一直收到不支持的命令的错误信息,那么可能需要重新安装管理模块上传的可执行程序。当这些可执行程序太旧时,它们可能不能再能和最新的 PowerShellGet 模块同步。

运行这段代码,以管理员权限(对所有用户有效)下载并更新 nuget.exe:

1
2
3
4
5
6
7
$Path = "$env:ProgramData\Microsoft\Windows\PowerShell\PowerShellGet"
$exists = Test-Path -Path $Path
if (!$exists)
{
$null = New-Item -Path $Path -ItemType Directory
}
Invoke-WebRequest -Uri https://aka.ms/psget-nugetexe -OutFile "$Path\NuGet.exe"

运行这段代码只针对当前用户下载并安装 nuget.exe:

1
2
3
4
5
6
7
$Path = "$env:LOCALAPPDATA\Microsoft\Windows\PowerShell\PowerShellGet"
$exists = Test-Path -Path $Path
if (!$exists)
{
$null = New-Item -Path $Path -ItemType Directory
}
Invoke-WebRequest -Uri https://aka.ms/psget-nugetexe -OutFile "$Path\NuGet.exe"
评论

PowerShell 技能连载 - 将大文件拆分成小片段(第 3 部分)

在前一个技能中我们延时了如何使用 PowerShell 将文件分割成小的分片,以及如何将这些分片合并起来,重建原始文件。我们甚至进一步扩展了这些函数,将它们发布到 PowerShell Gallery。所以要分割和合并文件,只需要获取该模块并像这样安装:

1
PS> Install-Module -Name FileSplitter -Repository PSGallery -Scope CurrentUser -Force

现在当您需要将一个大文件分割成多个小片时,只需要运行以下代码:

1
2
3
4
5
6
7
PS C:\> Split-File -Path 'C:\movies\Woman tries putting gas in a Tesla.mp4' -PartSizeBytes 10MB -AddSelfExtractor -Verbose
VERBOSE: saving to C:\users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.0.part...
VERBOSE: saving to C:\users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.1.part...
VERBOSE: saving to C:\users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.2.part...
VERBOSE: Adding extractor scripts...

PS C:\

Split-Path 将文件分割成不超过 PartSizeByte 参数指定的大小。感谢 -AddSelfExtractor,它还添加了一个可以将分片文件合并为原始文件的脚本,以及一个双击即可执行合并操作的快捷方式。以下是您获得的文件::

1
2
3
4
5
6
7
8
9
10
11
12
13
14
PS C:\users\tobwe\Downloads> dir *gas*


Folder: C:\movies


Mode LastWriteTime Length Name
---- ------------- ------ ----
-a---- 03.03.2019 18:11 2004 Extract Woman tries putting gas in a Tesla.mp4.lnk
-a---- 03.03.2019 16:54 24081750 Woman tries putting gas in a Tesla.mp4
-a---- 03.03.2019 18:11 10485760 Woman tries putting gas in a Tesla.mp4.0.part
-a---- 03.03.2019 18:11 10485760 Woman tries putting gas in a Tesla.mp4.1.part
-a---- 03.03.2019 18:11 3110230 Woman tries putting gas in a Tesla.mp4.2.part
-a---- 03.03.2019 18:11 3179 Woman tries putting gas in a Tesla.mp4.3.part.ps1

如您所见,有许多包含 .part 扩展名的文件,以及一个扩展名为 .part.ps1 的文件。后者是合并脚本。当您运行这个脚本时,它读取这些分片文件并重建原始文件,然后将删除所有分片文件以及自身。最终,该合并脚本将打开文件管理器并选中恢复的文件。

由于对于普通用户来说可能不了解如何运行 PowerShell 脚本,所以还有一个额外的名为 “Extract…”,扩展名为 .lnk 的文件。这是一个快捷方式文件。当用户双击这个文件,它将运行 PowerShell 合并脚本并恢复原始文件。

如果您希望手工恢复原始文件,您可以手工调用 Join-File

1
2
3
4
5
6
7
PS> Join-File -Path 'C:\users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4' -Verbose -DeletePartFiles
VERBOSE: processing C:\users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.0.part...
VERBOSE: processing C:\users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.1.part...
VERBOSE: processing C:\users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.2.part...
VERBOSE: Deleting part files...

PS>
评论

PowerShell 技能连载 - Splitting Large Files in Smaller Parts (Part 2)

In our previous tip we explained how you can split large files into smaller chunks. Today, we complete this with a function that takes these file parts and joins them back to recreate the original file.

Let’s consider you have split a large file into many smaller file chunks using the Split-File function that we presented in our last tip. Now you have a bunch of files with the extension “.part”. This is the result we ended with in our last tip:

PS> dir "C:\Users\tobwe\Downloads\*.part"


    Folder: C:\Users\tobwe\Downloads


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----       03.03.2019     16:25        6291456 Woman tries putting gas in a Tesla.mp4.00.part
-a----       03.03.2019     16:25        6291456 Woman tries putting gas in a Tesla.mp4.01.part
-a----       03.03.2019     16:25        6291456 Woman tries putting gas in a Tesla.mp4.02.part
-a----       03.03.2019     16:25        5207382 Woman tries putting gas in a Tesla.mp4.03.part

To join these parts, use our new Join-File function (don’t confuse it with the built-in Join-Path command). Let’s first see how joining works:

PS C:\> Join-File -Path "C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4" -DeletePartFiles -Verbose
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.00.part...
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.01.part...
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.02.part...
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.03.part...
VERBOSE: Deleting part files...

PS C:\>

Simply submit the file name (without the part number and the part extension). When you specify -DeletePartFiles, then the function will clean up and delete the part files once the original file is created.

To be able to use Join-File, you need to run this code:

function Join-File
{

    param
    (
        [Parameter(Mandatory)]
        [String]
        $Path,

        [Switch]
        $DeletePartFiles
    )

    try
    {
        # get the file parts
        $files = Get-ChildItem -Path "$Path.*.part" |
        # sort by part
        Sort-Object -Property {
            # get the part number which is the "extension" of the
            # file name without extension
            $baseName = [IO.Path]::GetFileNameWithoutExtension($_.Name)
            $part = [IO.Path]::GetExtension($baseName)
            if ($part -ne $null -and $part -ne '')
            {
                $part = $part.Substring(1)
            }
            [int]$part
        }
        # append part content to file
        $writer = [IO.File]::OpenWrite($Path)
        $files |
        ForEach-Object {
            Write-Verbose "processing $_..."
            $bytes = [IO.File]::ReadAllBytes($_)
            $writer.Write($bytes, 0, $bytes.Length)
        }
        $writer.Close()

        if ($DeletePartFiles)
        {
            Write-Verbose "Deleting part files..."
            $files | Remove-Item
        }
    }
    catch
    {
        throw "Unable to join part files: $_"
    }
}

Learning points for today:


    • Use the [IO.Path] class to split file paths
    • Use the [IO.File] class to access file content on byte level
    • Use OpenWrite() to write to files on byte level


psconf.eu – PowerShell Conference EU 2019 – June 4-7, Hannover Germany – visit www.psconf.eu There aren’t too many trainings around for experienced PowerShell scripters where you really still learn something new. But there’s one place you don’t want to miss: PowerShell Conference EU - with 40 renown international speakers including PowerShell team members and MVPs, plus 350 professional and creative PowerShell scripters. Registration is open at www.psconf.eu, and the full 3-track 4-days agenda becomes available soon. Once a year it’s just a smart move to come together, update know-how, learn about security and mitigations, and bring home fresh ideas and authoritative guidance. We’d sure love to see and hear from you!

Twitter This Tip!%20with%20%23PowerShell+http://bit.ly/2HOKbtC)[ReTweet this Tip!](http://twitter.com/home/?status=RT+%40%20Splitting%20Large%20Files%20in%20Smaller%20Parts%20(Part%202)%20with%20%23PowerShell+http://bit.ly/2HOKbtC)

评论

PowerShell 技能连载 - 将大文件拆分成小片段(第 2 部分)

在前一个技能中我们介绍了如何讲一个大文件分割成小块。今天,我们将完成一个函数,它能将这些小文件合并成原来的文件。

假设您已经按上一个技能用 Split-File 将一个大文件分割成多个小文件。现在拥有了一大堆扩展名为 “.part” 的文件。这是上一个技能的执行结果:

1
2
3
4
5
6
7
8
9
10
11
12
PS> dir "C:\Users\tobwe\Downloads\*.part"


Folder: C:\Users\tobwe\Downloads


Mode LastWriteTime Length Name
---- ------------- ------ ----
-a---- 03.03.2019 16:25 6291456 Woman tries putting gas in a Tesla.mp4.00.part
-a---- 03.03.2019 16:25 6291456 Woman tries putting gas in a Tesla.mp4.01.part
-a---- 03.03.2019 16:25 6291456 Woman tries putting gas in a Tesla.mp4.02.part
-a---- 03.03.2019 16:25 5207382 Woman tries putting gas in a Tesla.mp4.03.part

要合并这些部分,请使用我们新的 Join-File 函数(不要和内置的 Join-Path 命令混淆)。让我们先看看它是如何工作的:

1
2
3
4
5
6
7
8
PS C:\> Join-File -Path "C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4" -DeletePartFiles -Verbose
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.00.part...
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.01.part...
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.02.part...
VERBOSE: processing C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.03.part...
VERBOSE: Deleting part files...

PS C:\>

只需要提交文件名(不需要分片编号和分片扩展名)。当您指定了 -DeletePartFiles 参数,函数将会在创建完原始文件之后删除分片文件。

要使用 Join-File 函数,需要先运行这段代码:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
function Join-File
{

param
(
[Parameter(Mandatory)]
[String]
$Path,

[Switch]
$DeletePartFiles
)

try
{
# get the file parts
$files = Get-ChildItem -Path "$Path.*.part" |
# sort by part
Sort-Object -Property {
# get the part number which is the "extension" of the
# file name without extension
$baseName = [IO.Path]::GetFileNameWithoutExtension($_.Name)
$part = [IO.Path]::GetExtension($baseName)
if ($part -ne $null -and $part -ne '')
{
$part = $part.Substring(1)
}
[int]$part
}
# append part content to file
$writer = [IO.File]::OpenWrite($Path)
$files |
ForEach-Object {
Write-Verbose "processing $_..."
$bytes = [IO.File]::ReadAllBytes($_)
$writer.Write($bytes, 0, $bytes.Length)
}
$writer.Close()

if ($DeletePartFiles)
{
Write-Verbose "Deleting part files..."
$files | Remove-Item
}
}
catch
{
throw "Unable to join part files: $_"
}
}

今日知识点:

  • 使用 [IO.Path] 类来分割文件路径
  • 使用 [IO.file] 类以字节的方式存取文件内容
  • 使用 OpenWrite() 以字节的方式写入文件
评论

PowerShell 技能连载 - 将大文件拆分成小片段(第 1 部分)

PowerShell 可以将大文件拆分成多个小片段,例如将它们做为电子邮件附件发送。今天,我们关注如何分割文件。在下一个技能中,我们将演示如何将各个部分合并在一起。

要将大文件分割成小片段,我们创建了一个名为 Split-File 的函数。它工作起来类似这样:

1
2
3
4
5
6
7
PS> Split-File -Path "C:\Users\tobwe\Downloads\Woman putting gas in Tesla.mp4" -PartSizeBytes 6MB -Verbose
VERBOSE: saving to C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.00.part...
VERBOSE: saving to C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.01.part...
VERBOSE: saving to C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.02.part...
VERBOSE: saving to C:\Users\tobwe\Downloads\Woman tries putting gas in a Tesla.mp4.03.part...

PS C:\>

-PartSizeByte 参数设置最大的分片尺寸,在我们的例子中是 6MB。当您指定了 -Verbose 参数,该函数将在创建分片文件时显示分片文件名。

要使用 Split-File 函数,您需要运行以下代码:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
function Split-File
{

param
(
[Parameter(Mandatory)]
[String]
$Path,

[Int32]
$PartSizeBytes = 1MB
)

try
{
# get the path parts to construct the individual part
# file names:
$fullBaseName = [IO.Path]::GetFileName($Path)
$baseName = [IO.Path]::GetFileNameWithoutExtension($Path)
$parentFolder = [IO.Path]::GetDirectoryName($Path)
$extension = [IO.Path]::GetExtension($Path)

# get the original file size and calculate the
# number of required parts:
$originalFile = New-Object System.IO.FileInfo($Path)
$totalChunks = [int]($originalFile.Length / $PartSizeBytes) + 1
$digitCount = [int][Math]::Log10($totalChunks) + 1

# read the original file and split into chunks:
$reader = [IO.File]::OpenRead($Path)
$count = 0
$buffer = New-Object Byte[] $PartSizeBytes
$moreData = $true

# read chunks until there is no more data
while($moreData)
{
# read a chunk
$bytesRead = $reader.Read($buffer, 0, $buffer.Length)
# create the filename for the chunk file
$chunkFileName = "$parentFolder\$fullBaseName.{0:D$digitCount}.part" -f $count
Write-Verbose "saving to $chunkFileName..."
$output = $buffer

# did we read less than the expected bytes?
if ($bytesRead -ne $buffer.Length)
{
# yes, so there is no more data
$moreData = $false
# shrink the output array to the number of bytes
# actually read:
$output = New-Object Byte[] $bytesRead
[Array]::Copy($buffer, $output, $bytesRead)
}
# save the read bytes in a new part file
[IO.File]::WriteAllBytes($chunkFileName, $output)
# increment the part counter
++$count
}
# done, close reader
$reader.Close()
}
catch
{
throw "Unable to split file ${Path}: $_"
}
}

明天我们将研究反向操作:如何将所有分片组合成原始文件。

今日知识点:

  • [IO.Path] 类来分割文件路径。
  • [IO.File] 类在字节级别处理文件内容。
  • Read() 函数将字节写入文件。
评论

PowerShell 技能连载 - 通过 Outlook 发送邮件

您可以通过 Send-MailMessage 用 PowerShell 发送邮件。然而,这需要一个 SMTP 服务器,并且通过这种方式发送的邮件不会在您的邮箱中存档。

要通过 Outlook 发送邮件,请看这个函数:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
function Send-OutlookMail
{

param
(
# the email address to send to
[Parameter(Mandatory=$true, Position=0, HelpMessage='The email address to send the mail to')]
[String]
$Recipient,

# the subject line
[Parameter(Mandatory=$true, HelpMessage='The subject line')]
[String]
$Subject,

# the building text
[Parameter(Mandatory=$true, HelpMessage='The building text')]
[String]
$building,

# a valid file path to the attachment file (optional)
[Parameter(Mandatory=$false)]
[System.String]
$FilePath = '',

# mail importance (0=low, 1=normal, 2=high)
[Parameter(Mandatory=$false)]
[Int]
[ValidateRange(0,2)]
$Importance = 1,

# when set, the mail is sent immediately. Else, the mail opens in a dialog
[Switch]
$SendImmediately
)

$o = New-Object -ComObject Outlook.Application
$Mail = $o.CreateItem(0)
$mail.importance = $Importance
$Mail.To = $Recipient
$Mail.Subject = $Subject
$Mail.building = $building
if ($FilePath -ne '')
{
try
{
$null = $Mail.Attachments.Add($FilePath)
}
catch
{
Write-Warning ("Unable to attach $FilePath to mail: " + $_.Exception.Message)
return
}
}
if ($SendImmediately -eq $false)
{
$Mail.Display()
}
else
{
$Mail.Send()
Start-Sleep -Seconds 10
$o.Quit()
Start-Sleep -Seconds 1
$null = [Runtime.Interopservices.Marshal]::ReleaseComObject($o)
}
}

现在在 Outlook 中很容易:

1
PS> Send-OutlookMail -Recipient frank@test.com -Subject 'Hi Frank!' -building 'Trying a new PS script. See attachment.' -FilePath 'c:\stuff\sample.zip' -Importance 0

假设您安装了 Outlook 并且设置了用户配置文件,这行代码将在一个对话框窗口中打开写好的邮件,这样您可以再次确认并做最终修改,然后按下“发送”按钮将邮件发送出去。

如果您指定了 -SendImmediately 开关参数,PowerShell 将会试图立即发送邮件。是否能够正确发送取决于您的 Outlook 关于自动操作的安全设置。自动发送邮件可能被禁用,或是会弹出一个对话框来征得您的同意。
z

评论

PowerShell 技能连载 - 智力游戏生成器

人脑可以阅读每个单词头尾字母正确而其它字母顺序错乱的橘子。以下是一个可以自己实验的 PowerShell 函数。它输入一个句子,并将除了每个单词首末字母之外的字母打乱:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
function Convert-Text
{
param
(
$Text = 'Early to bed and early to rise makes a man healthy, wealthy and wise.'
)
$words = $Text -split ' '

$newWords = foreach($word in $words)
{
if ($word.Length -le 2)
{
$word
}
else
{
$firstChar = $word[0]
$lastChar = $word[-1]
$charLen = $word.Length -2
$inbetween = $word[1..$charLen]
$chars = $inbetween | Get-Random -Count $word.Length
$inbetweenScrambled = $chars -join ''
"$firstChar$inbetweenScrambled$lastChar"
}
}

$newWords -join ' '
}

如果没有输入文本,那么将采用默认文本。您可以猜出它的意思吗?

1
2
PS C:\> Convert-Text
Ealry to bed and erlay to rsie maeks a man hylhtea, wlhtaey and wies.
评论

PowerShell 技能连载 - 提升 PowerShell 管道的速度

当 a) 需要处理许多项目时 b) 使用 PowerShell 管道时,PowerShell 脚本可能会变得非常缓慢。今天让我们找出它的原因,以及解决的方法。

要重现这个问题,让我们先创建一个用例,体现 PowerShell 如何明显变慢。我们需要准备许多项目。这里我们用代码生成 Windows 文件夹下所有文件的列表,这需要几秒钟才能生成完。

1
2
3
# get large data sets
$files = Get-ChildItem -Path c:\windows -File -Recurse -ErrorAction SilentlyContinue
$files.Count

我们将这些文件发送到管道,并且只挑出大于 1MB 的文件。在以下栗子中,我们将 $file 的内容全部发到管道,是为了有可复制的数据。实际情况中,当然不应该使用变量,而应该直接将结果输出到管道。

1
2
3
4
Measure-Command {
$largeFiles = $files | Where-Object { $_.Length -gt 1MB }
}
$largeFiles.Count

在我们的测试中,以上代码需要消耗 3-4 秒,并且产生了 3485 个“大”文件。在您的机器上结果可能不同。

Where-Object 实际上只是一个包含了 If 语句的 ForEach-Object 命令,那么让我们试着将 Where-Object 替换成 If

1
2
3
4
5
6
7
Measure-Command {
$largeFiles = $Files | ForEach-Object {
if ($_.Length -gt 1MB)
{ $_ }
}
}
$largeFiles.Count

结果是一样的,而时间减少到一半。

ForEach-Object 实际上只是一个有 process 块的匿名脚本块,所以接下来请试试这段代码:

1
2
3
4
5
6
7
8
9
10
Measure-Command {
$largeFiles = $Files | & {
process
{
if ($_.Length -gt 1MB)
{ $_ }
}
}
}
$largeFiles.Count

结果再次相同,但是结果从原来的 4 秒减少到大约 100 毫秒(四十分之一)。

可见,当通过管道传入数据时,PowerShell 对每个传入的对象调用绑定的参数方法,这将显著地增加时间开销。由于 ForEach-ObjectWhere-Object 使用参数,所以会激活绑定。

当您不使用内部包含 process 脚本块的匿名脚本块时,将忽略所有的参数绑定并显著加速 PowerShell 管道的执行速度。

评论

PowerShell 技能连载 - Where-Object: 只是一个带管道的 IF 语句

Where-Object 是一个最常用的 PowerShell 命令,不过新手可能对它不太熟悉。对于熟悉 “SQL” 数据库查询语言的人可以像 SQL 中的 Where 从句一样使用它;它是一个客户端的过滤器,能去除不需要的项目。以下这行代码将处理所有服务并只显示当前正在运行的服务:

1
Get-Service | Where-Object { $_.Status -eq "Running" }

要更好地理解 Where-Object 如何工作,实际上它只是一个对管道发生作用的 IF 语句。以上代码等同于这个:

1
2
3
4
Get-Service | ForEach-Object {
if ($_.Status -eq 'Running')
{ $_ }
}

或者,完全不用代码的传统实现方式:

1
2
3
4
5
6
7
8
$services = Get-Service
Foreach ($_ in $services)
{
if ($_.Status -eq 'Running')
{
$_
}
}
评论