关于 PowerShell Copy-Item 命令的快速问题。我想知道您是否有一个目录结构并想覆盖另一个目录结构，有没有办法在“预览”模式下运行 Copy-Item 命令。它将输出从目录 a 覆盖的文件到目录 b 但实际上不执行 Copy-Item 命令。
任何帮助或建议表示赞赏。
谢谢。
【问题讨论】：
-WhatIf 运行Copy-Item。但是，对于您要实现的目标，robocopy 将是一个更合适的工具。添加参数/l 进行试运行。
标签： powershell
tl;dr：
Copy-Item -WhatIf 不会为您提供所需的详细程度 - 见下文。
改用robocopy.exe -l（仅限Windows），正如Ansgar Wiechers 建议的那样，因为它单独列出了将复制的文件，包括动态省略那些已经存在于目标目录（默认情况下具有相同的大小和上次修改的时间戳）。
robocopy 比Copy-Item 更快，功能更全，并且避免了a notable pitfall of the latter。Get-Help about_CommonParameters 记录了许多（但不是全部）cmdlet 支持的-WhatIf 通用参数，其目的是预览操作 没有实际执行。
但是，此功能是以抽象方式实现的，并且通常无法提供人们希望的详细信息。
恰当的例子：虽然Copy-Item 确实支持-WhatIf，但它可能无法为您提供所需的详细程度，因为如果源项目是一个目录，仅输出 单行 行，如下所示：
What if: Performing the operation "Copy Directory" on target "Item: sourceDir Destination: destDir".
请注意，无论您的 Copy-Item 调用是否包含 -Recurse 开关，您都会看到同一行。
即使您手动确保目标目录存在并将/* 附加到源目录路径以查看单个文件名，您也只能在 child 级别看到它们，而不是进一步沿着子树向下，你永远不会得到 robocopy -l 提供的关于哪些文件实际需要替换的动态信息。
【讨论】：
有趣的问题！ 这是我在 Powershell 中完成这一切的尝试，因此不需要 RoboCopy。
function Copy-Preview {
[CmdletBinding(DefaultParameterSetName = 'ByPath')]
param(
[Parameter(ValueFromPipeline = $true, Mandatory = $true, ParameterSetName = 'ByPath', Position = 0)]
[ValidateScript({ Test-Path $_ })]
[string]$Path,
[Parameter(ValueFromPipeline = $true, Mandatory = $true, ParameterSetName = 'ByLiteralPath', Position = 0)]
[ValidateScript({ Test-Path $_ })]
[string]$LiteralPath,
[Parameter(ValueFromPipeline = $true, Mandatory = $true, Position = 1)]
[string]$Destination,
[string]$Filter = $null,
[string]$Include = $null,
[string]$Exclude = $null,
[switch]$Recurse,
[switch]$Force
)
if ($PSCmdlet.ParameterSetName -eq 'ByLiteralPath') { $Path = $LiteralPath }
# determine if $Path and $Destination hold a file or a directory
$srcIsFolder = (Test-Path $Path -PathType Container -ErrorAction SilentlyContinue)
# cannot use Test-Path here because then the path has to exist.
# assume if it has an extension the path is a file, otherwise a directory
# NOTE:
# This is certainly not fullproof, so to avoid problems, always make sure
# the destination ends with a backslash if a directory is intended.
$destIsFolder = (-not ([System.IO.Path]::HasExtension($Destination)))
if ($destIsFolder -and !(Test-Path $Destination -PathType Container)) {
Write-Host "Destination path does not exist yet. All files from '$Path' will be copied fresh" -ForegroundColor Green
return
}
elseif ($srcIsFolder -and (!$destIsFolder)) {
# should not happen: source is a directory, while the destination is a file..
Write-Error "When parameter Path points to a directory, the Destination cannot be a file.."
return
}
$count = 0
if ($srcIsFolder -and $destIsFolder) {
# Both the source and the destinations are folders
# make sure both paths are qualified for .Replace() further down
if (-not $Path.EndsWith("\")) { $Path += "\" }
if (-not $Destination.EndsWith("\")) { $Destination += "\" }
$splat = @{
Filter = $Filter
Include = $Include
Exclude = $Exclude
Recurse = $Recurse
Force = $Force
}
# add either Path or LiteralPath to the parameters as they are mutually exclusive
if ($PSCmdlet.ParameterSetName -eq 'ByPath') { $splat.Path = $Path }
else { $splat.LiteralPath = $LiteralPath }
$srcFiles = Get-ChildItem @splat | Select-Object -ExpandProperty FullName
# reuse the splat parameters hash for the destination, but change the Path
if ($splat.LiteralPath) {($splat.Remove("LiteralPath"))}
$splat.Path = $Destination
$destFiles = Get-ChildItem @splat | Select-Object -ExpandProperty FullName
foreach ($srcItem in $srcFiles) {
$destItem = $srcItem.Replace($Path, $Destination)
if ($destFiles -contains $destItem) {
Write-Host "'$destItem' would be overwritten"
$count++
}
}
}
elseif (!$srcIsFolder) {
# the source is a file
if (!$destIsFolder) {
# the destination is also a file
if (Test-Path $Destination -PathType Leaf) {
Write-Host "'$Destination' would be overwritten"
$count++
}
}
else {
# source is file, destination is a directory
$destItem = Join-Path $Destination (Split-Path $Path -Leaf)
if (Test-Path $destItem -PathType Leaf) {
Write-Host "'$destItem' would be overwritten"
$count++
}
}
}
$msg = "$count item{0} would be overwritten by Copy-Item" -f $(if ($count -ne 1) { 's' })
$dash = "-" * ($msg.Length)
Write-Host "$dash`r`n$msg" -ForegroundColor Green
}
【讨论】：
您可以使用 -whatif 参数。
Copy-item -path myfile.txt -destination myfoldertoCopyTo\ -whatif
【讨论】：
-WhatIf 没有提供。