如何在powershell中递归附加到文件名？

Question

I have multiple .txt files in folders/their sub-folders.

I want to append _old to their file names.

I tried:

Get-ChildItem -Recurse | Rename-Item -NewName {$_.name -replace '.txt','_old.txt' }

This results in:

1. Some files get updated correctly
2. Some files get updated incorrectly - they get _old twice - example: .._old_old.txt
3. There are few errors: Rename-Item : Source and destination path must be different.

Answer 1

To prevent already renamed files from accidentally reentering the file enumeration and therefore getting renamed multiple times, enclose your Get-ChildItem call in () , the grouping operator , which ensures that all output is collected first ^[1] , before sending the results through the pipeline:

(Get-ChildItem -Recurse) |
  Rename-Item -NewName { $_.name -replace '\.txt$', '_old.txt' }

Note that I've used \\.txt$ as the regex ^[2] , so as to ensure that only a literal . ( \\. ) followed by string txt at the end ( $ ) of the file name is matched, so as to prevent false positives (eg, a file named Atxt.csv or even a directory named AtxtB would accidentally match your original regex).

Note: The need to collect all Get-ChildItem output first arises from how the PowerShell pipeline fundamentally works: objects are (by default) sent to the pipeline one by one , and processed by a receiving command as they're being received . This means that, without (...) around Get-ChildItem , Rename-Item starts renaming files before Get-ChildItem has finished enumerating files, which causes problems. See this answer for more information about how the PowerShell pipeline works.
^{Tip of the hat to Matthew for suggesting inclusion of this information.}

However, I suggest optimizing your command as follows:

(Get-ChildItem -Recurse -File -Filter *.txt) | 
  Rename-Item -NewName { $_.BaseName + '_old' + $_.Extension }

• -File limits the the output to files (doesn't also return directories ).

• -Filter is the fastest way to limit results to a given wildcard pattern.

• $_.BaseName + '_old' + $_.Extension uses simple string concatenation via the sub-components of a file name.

  • An alternative is to stick with -replace :
    $_.Name -replace '\\.[^.]+$', '_old$&'

Note that if you wanted to run this repeatedly and needed to exclude files renamed in a previous run, add -Exclude *_old.txt to the Get-ChildItem call.

---

^{[1] Due to a change in how Get-ChildItem is implemented in PowerShell [Core] 6+ (it now internally sorts the results, which invariably requires collecting them all first), the (...) enclosure is no longer strictly necessary , but this could be considered an implementation detail, so for conceptual clarity it's better to continue to use (...) .}

^{[2] PowerShell's -replace operator operates on regexes (regular expressions); it doesn't perform literal substring searches the way that the [string] type's .Replace() method does.}

Answer 2

The below command will return ALL files from the current folder and sub-folders within the current directory the command is executed from.

Get-ChildItem -Recurse

Because of this you are also re-turning all the files you have already updated to have the _old suffix.

What you need to do is use the -Include -Exclude paramters of the Get-Childitem Cmdlet in order to ignore files that already have the _old suffix, and meet your include criteria, for example.

Get-ChildItem -Recure -Include "*.txt" -Exclude "*_old"

Then pipe the results into your re-name item command

Get-ChildItem cmdlet explanation can be found here.

https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.management/get-childitem?view=powershell-7