Insert string into multiple filenames

Issue

I have multiple files named in this format:

Fat1920OVXPlacebo_S20_R1_001.fastq
Kidney1235SHAM_S65_R1_001.fastq
Kidney1911OVXPlacebo_S94_R2_001.fastq
Liver1289OVXEstrogen_S24_R2_001.fastq

I need to insert the string "L1000_" into their names so that they read

Fat1920OVXPlacebo_S20_L1000_R1_001.fastq
Kidney1235SHAM_S65_L1000_R1_001.fastq
Kidney1911OVXPlacebo_S94_L1000_R2_001.fastq
Liver1289OVXEstrogen_S24_L1000_R2_001.fastq

I apologize but I have absolutely no experience in coding in powershell. The closest thing I could find to do this was a script that renames the entire file:

Set objFso = CreateObject(“Scripting.FileSystemObject”)

Set Folder = objFSO.GetFolder(“ENTER\PATH\HERE”)

For Each File In Folder.Files

    sNewFile = File.Name

    sNewFile = Replace(sNewFile,”ORIGINAL”,”REPLACEMENT”)

    if (sNewFile<>File.Name) then

        File.Move(File.ParentFolder+”\”+sNewFile)

    end if

Next

however, I just need to insert a string at a specific place in the file’s title. I have 257 files and do not want to go 1 by 1. Does anyone have an idea on how to run this in windows?

Solution

Use Get-ChildItem to enumerate the files of interest, pipe them to Rename-Item, and use a delay-bind script block ({ ... }) to dynamically determine the new name, via a regex-based -replace operation.

(Get-ChildItem $yourFolder -Filter *.fastq) |
  Rename-Item -NewName { $_.Name -replace '(?<=_S\d+_)', 'L1000_' } -WhatIf

^{Note:
• The -WhatIf common parameter in the command above previews the operation. Remove -WhatIf once you’re sure the operation will do what you want.
• Even though not strictly necessary in this case, enclosing the Get-ChildItem command in (...), the grouping operator ensures that already renamed files don’t accidentally re-enter the enumeration of files to be renamed – see this answer.}

• (?<=_S\d+_) uses a positive look-behind assertion ((?<=...)) to match verbatim string _S, followed by one or more (+) digits (\d), followed by verbatim _.

• Since the look-behind assertion merely matches a position in the string rather than a substring, the replacement operand, verbatim L1000_ in this case, is inserted at that position in (a copy of) the input string.

• For a more detailed explanation of the delay-bind script-block technique, see this answer.

Answered By – mklement0

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