How to add a symbol in a middle of a file name in PS

Question

I have modified several thousand files with a various things requested by the owners. Now, I need to add one final thing and I am not 100% on how to do it.

Scenario is as follows - all files have a 10 digit number at the start, I need to add a hyphen after the number. String is a variable but it is always the same length. 1234567890abcdefgh.xls would be an example

I have used GCI to make changes to symbols and static parts but not sure how to call for insertion in a specific place of a file (after the 10th character of a variable string)

Any ideas would be most welcome!

Answer 1

You can use the $matches you get from the capturing groups of a -match comparison:

(Get-ChildItem -Path 'X:\WhereTheFilesAre' -File) | 
Where-Object { $_.BaseName -match '^(\d{10})([^-].*)' } |
Rename-Item -NewName { '{0}-{1}{2}' -f $matches[1], $matches[2], $_.Extension }

or by using the Substring() method:

(Get-ChildItem -Path 'X:\WhereTheFilesAre' -File) | 
Where-Object { $_.BaseName -match '^\d{10}[^-]' } |
Rename-Item -NewName { $_.Name.Substring(0,10) + '-' + $_.Name.Substring(10) }

or use the regex -replace operator:

(Get-ChildItem -Path 'X:\WhereTheFilesAre' -File) | 
Where-Object { $_.BaseName -match '^\d{10}[^-]' } |
Rename-Item -NewName { $_.Name -replace '^(\d{10})', '$1-' }

Answer 2

You can use string.Insert() to insert a string into another at a specific offset:

PS ~> '1234567890abcdefgh.xls'.Insert(10, '-')
1234567890-abcdefgh.xls

To apply to all files in a directory, you could do something like this:

Get-ChildItem -File |Where-Object Name -match '^\d{10}[^-]' |Rename-Item -NewName { $_.Name.Insert(10, '-') }

The regular expression pattern ^\d{10}[^-] will only match file names that start with 10 digits followed by something other than a hyphen (to avoid renaming files that already comply with the naming convention)