根据基本名称的x个数字字符分组项目 [英] Group items based on x number characters of basename

问题描述

我得到了帮助来设置一个巧妙的脚本，该脚本根据基本名称和LastWriteTime对文件夹中的项目进行分组，它使我可以删除除给定数量的文件(即5个版本)以外的所有内容.现在，我想将基本名称分组限制为8个字符.

I got help to setup a clever script that groups items in a folder based on basename and LastWriteTime it lets me delete everything except given number of files (i.e 5 versions). Now I'd like to limit basename grouping to 8 characters.

gci C:\test\ |
where{-not $_.PsIsContainer} |
$file = basename
Group-Object $file.substring(8) |
foreach {
  $_.Group |
  sort LastWriteTime -Descending |
  Select -Skip 5 |
   foreach { Remove-Item $_.fullname -Force -WhatIf }
  }

由于我真的是Powershell的新手，所以不确定上面的方法是否正确.

As I'm really new to powershell I'm not sure if above is correct approach.

推荐答案

如果要按前8个字符分组，则需要 Substring(0，8). Substring(8)将产生从第9个字符到字符串结尾的子字符串.另外，如果要按当前对象的属性分组，则可以在脚本块中定义它们.

If you want to group by the first 8 characters, you need Substring(0, 8). Substring(8) will produce the substring from the 9th character to the end of the string. Also, if you want to group by properties of the current object, you define them in a scriptblock.

更改此:

gci C:\test\ |
where{-not $_.PsIsContainer} |
$file = basename
Group-Object $file.substring(8) | ...

对此:

Get-ChildItem 'C:\test' |
  Where-Object {-not $_.PSIsContainer} |
  Group-Object { $_.Basename.Substring(0,8) } | ...

请注意，如果基本名称少于8个字符，则 Substring(0,8)将引发错误.例如，可以通过将长度定义为最小值8和字符串长度来避免这种情况:

Note that Substring(0,8) will throw an error if the basename is shorter than 8 characters. You can avoid that for instance by defining the length as the minimum of 8 and string length:

$_.Basename.Substring(0, [Math]::Min(8, $_.Basename.Length))

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