powershell - 选择对象的协助-最后1个和文件名

Question

我有以下代码，用于检查目录中的“a_file.xls”，“b_file.xls”，“c_file.xls”等。

根据找到的内容，它将“file.xls”重命名为下一个字母，例如，如果找到了上述三个A，B，C文件，则下次“file.xls”重命名时将变为“d_file.xls”

我需要修改此代码以使用$fileDate = (get-date).ToString('MMdd')在重命名的文件中包含日期戳

这是执行我上面描述的代码。

$fileDate = (get-date).ToString('MMdd')

$dir = "\\server\folder123"

$var = (Get-ChildItem -Path $dir\*_file.xls | Select-Object -Last 1).BaseName.Split('_')[0]

switch ($var) {
   "a" {$fileLetter = "b"; break}
   "b" {$fileLetter = "c"; break}
   "c" {$fileLetter = "d"; break}
   "d" {$fileLetter = "e"; break}
   "e" {$fileLetter = "f"; break}
   "f" {$fileLetter = "g"; break}
   "g" {$fileLetter = "h"; break}
   "h" {$fileLetter = "i"; break}
   "i" {$fileLetter = "j"; break}
   "j" {$fileLetter = "k"; break}
   "k" {$fileLetter = "l"; break}
   "l" {$fileLetter = "m"; break}
   "m" {$fileLetter = "n"; break}
   "n" {$fileLetter = "o"; break}
   "o" {$fileLetter = "p"; break}
   "p" {$fileLetter = "q"; break}
   "q" {$fileLetter = "r"; break}
   "r" {$fileLetter = "s"; break}
   "s" {$fileLetter = "t"; break}
   "t" {$fileLetter = "u"; break}
   "u" {$fileLetter = "v"; break}
   "v" {$fileLetter = "w"; break}
   "w" {$fileLetter = "x"; break}
   "x" {$fileLetter = "y"; break}
   "y" {$fileLetter = "z"; break}
   default {$fileLetter = "a"; break}
}
$renameFrom = $dir + "\file.xls"
$renameTo = $fileLetter + "_file.xls"

Rename-item $dir\"file.xls" $renameTo

$ renameTo将成为... $renameTo = $fileDate + $fileLetter + "_file.xls"
当我改成这个字母时，我的 Select-Object -Last 1变成了一个问题，它找不到上次使用的字母。相反，它只是找到file.xls作为最后一个，然后尝试重命名为已经存在的文件:示例1120a_file.xls。

我怎样才能解决这个问题？我用正则表达式模式尝试了 | select-string，但是没有用。还使用正则表达式尝试了 | Where-Object，但也不起作用。

关于如何最好地实现这一目标的任何建议？

发生的事情是我正在解压缩包含file.xls的文件，可能有多个文件，有时没有。需要将文件重命名为MMddA_File.xls，MMddB_File.xls，MMddC_File.xls等。

Answer 1

如果您只关心文件名中的字母，而不关心时间戳，则可以尝试以下操作:

# Extract the alphabetically highest letter from the existing file names.
# * -creplace '.*([a-z])_.*', '$1' matches each base name in full,
#   and captures a lowercase letter before "_" in the 1st capture group,
#   which is then used to replace the input string ('$1'), effectively
#   returning only the letter from each base name.
# * The letters are then sorted in descending order, and the first one
#   (the highest) is returned.
$fileLetter = 
  (Get-Item -Path $dir\*_file.xls).BaseName -creplace '.*([a-z])_.*', '$1' | 
    Sort-Object -Descending | 
      Select-Object -First 1

# Increment the highest letter by 1 (the next letter, alphabetically).
$fileLetter = if (-not $fileLetter -or $fileLetter.Length -gt 1) {
    'a'
  } else {
    [char] (1 + [char] $fileLetter)
  }

$renameFrom = $dir + "\file.xls"
$renameTo = (Get-Date).ToString('MMdd') + $fileLetter + "_file.xls"

Rename-Item $renameFrom $renameTo -WhatIf

注意:上面命令中的 -WhatIf common parameter预览操作。确定操作将执行所需操作后，删除 -WhatIf。