How to bulk rename files to add a missing comma before the first space

Question

I have a folder with hundreds of files that are supposed to be to this standard:

Lastname, Firstname - 1010 ddmmyy.pdf

At least half of them are missing that comma, and I need it added to them all.

Using something like this replaces all spaces with a comma, which is not what I need.

Get-ChildItem -Name *.pdf | Rename-Item -NewName { $_ -replace ' ',',' }

I'm stuck! Is there a way to identify inserting a single comma at the beginning of the first blank space?

Answer 1

You can use below to do that:

Get-ChildItem -Path 'D:\SomeWhere' -Filter '*.pdf' -File | Rename-Item -NewName { $_.Name -replace '^([^,\s]+)\s+(.+)', '$1, $2' }

Regex details:

^               Assert position at the beginning of the string
(               Match the regular expression below and capture its match into backreference number 1
   [^,\s]       Match a single character NOT present in the list below
                The character “,”
                A whitespace character (spaces, tabs, line breaks, etc.)
      +         Between one and unlimited times, as many times as possible, giving back as needed (greedy)
)              
\s              Match a single character that is a “whitespace character” (spaces, tabs, line breaks, etc.)
   +            Between one and unlimited times, as many times as possible, giving back as needed (greedy)
(               Match the regular expression below and capture its match into backreference number 2
   .            Match any single character that is not a line break character
      +         Between one and unlimited times, as many times as possible, giving back as needed (greedy)
)

Answer 2

You could try filtering for all the .pdf that have a space in their name then adding a condition to check if the file already contains a , in it's Name, if it does skip and if it doesn't, replace the first space white space followed by everything else with a , plus all the replaced string, i.e.:

Get-ChildItem -Filter '* *.pdf' | ForEach-Object {
    if(-not $_.BaseName.Contains(',')) {
        $_ | Rename-Item -NewName { $_.Name -replace '\s.+', ',$0' }
    }
}

Answer 3

Another regex solution based on the -replace operator, a streamlined version of Theo's helpful answer:

Get-ChildItem -Filter *.pdf | 
  Rename-Item -NewName { $_.Name -replace '^[^, ]+(?= )', '$&,' }

As an aside:

• There is an incidental problem with your attempt in that you're mistakenly using the -Name parameter, which, as a switch parameter (flag), is a stand-alone parameter not related to your *.pdf argument, which is therefore a positional argument that implicitly binds to the -Path parameter.

• Thus, since -Path also understands wildcards, simply removing -Name (which makes Get-ChildItem output relative path strings instead of [System.IO.FileInfo] instances) would have sufficed, but for performance reasons it is preferable to perform wildcard-based filtering with the -Filter parameter, as shown above. Slight caveat: While this typically works as intended, -Filter does not use PowerShell's wildcard expressions: it uses the wildcard matching of the file-system APIs, which have fewer features and legacy quirks - see this answer.

The basic idea is that if the word before the first space doesn't contain a comma, insert one right after it:

• Regex:

  • ^[^, ]+ matches one or more (+) characters (inside [...]) that are not (^) a , or a (space), at the start of the string (the first ^).

  • (?= ) is a look-ahead assertion that requires that a (space) follow what was matched before, without getting captured as part of the match.

• Replacement operand:

  • $& refers to the substring that matched the whole regex, and following it with a , is what inserts the desired comma.

Note:

• It is safe to unconditionally apply the -replace operation: if the file name doesn't match, the regex, it is returned as-is, and Rename-Item quietly ignores attempts to rename a file to the same name it already has.

• Unfortunately, Rename-Item does not do that for directories and reports an error instead - see GitHub issue #14903.

Answer 4

What about this (to be executed in a Windows Command Prompt, due to the tag cmd, at least in revision 2 of the question):

for /F "tokens=1* eol=  delims= " %I in ('dir /B /A:-D-H-S "* *.pdf" ^| findstr /R /I /C:"^[^, ][^, ]* [^ ]"') do @ren "%I %J" "%I, %J"

How it works:

• dir "* *.pdf" returns files whose names contain at least a SPACE;
• a pipe (|) redirects the list of file names into the next command,
• which is findstr; the search expression narrows the list to items beginning with a string neither containing SPACE nor ,, followed by a SPACE, followed by anything but a SPACE;
• the resulting list is captured by a for /F loop, that iterates over it, splitting the names into the part before (in %I) and the one after (in %J) the first SPACE;
• ren finally renames the files, inserting the desired , before the first SPACE;