Powershell - How to create array of filenames based on filename? - powershell

Question

I'm looking to create an array of files (pdf's specifically) based on filenames in Powershell. All files are in the same directory. I've spent a couple of days looking and can't find anything that has examples of this or something that is close but could be changed. Here is my example of file names:
AR - HELLO.pdf
AF - HELLO.pdf
RT - HELLO.pdf
MH - HELLO.pdf
AR - WORLD.pdf
AF - WORLD.pdf
RT - WORLD.pdf
HT - WORLD.pdf
....
I would like to combine all files ending in 'HELLO' into an array and 'WORLD' into another array and so on.
I'm stuck pretty early on in the process as I'm brand new to creating scripts, but here is my sad start:
Get-ChildItem *.pdf
Where BaseName -match '(.*) - (\w+)'
Updated Info...
I do not know the name after the " - " so using regex is working.
My ultimate goal is to combine PDF's based on the matching text after the " - " in the filename and the most basic code for this is:
$file1 = "1 - HELLO.pdf"
$file2 = "2 - HELLO.PDF"
$mergedfile = "HELLO.PDF"
Merge-PDF -InputFile $file1, $file2 -OututFile $mergedfile
I have also gotten the Merge-PDF to work using this code which merges all PDF's in the directory:
$Files = Get-ChildItem *.pdf
$mergedfiles = "merged.pdf"
Merge-PDF -InputFile $Files -OutputFile $mergedfiles
Using this code from #Mathias the $suffix portion of the -OutputFile works but the -InputFile portion is returning an error "Exception calling "Close" with "0" argument(s)"
$groups = Get-ChildItem *.pdf |Group-Object {$_.BaseName -replace
'^.*\b(\w+)$','$1'} -AsHashTable
foreach($suffix in $groups.Keys) {Merge-PDF -InputFile $(#($groups[$suffix]))
-OutputFile "$suffix.pdf"}
For the -InputFile I've tried a lot of different varieties and I keep getting the "0" arguments error. The values in the Hashtable seem to be correct so I'm not sure why this isn't working.
Thanks

Answer 1

This should do the trick:
$HELLO = Get-ChildItem *HELLO.pdf |Select -Expand Name
$WORLD = Get-ChildItem *WORLD.pdf |Select -Expand Name
If you want to group file names by the last word in the base name and you don't know them up front, regex is indeed an option:
$groups = Get-ChildItem *.pdf |Group-Object {$_.BaseName -replace '^.*\b(\w+)$','$1'} -AsHashTable
And then you can do:
$groups['HELLO'].Name
for all the file names ending with the word HELLO, or, to iterate over all of them:
foreach($suffixGroup in $groups.GetEnumerator()){
Write-Host "There are $($suffixGroup.Value.Count) files ending in $($suffixGroup.Key)"
}

Answer 2

Another option is to get all items with Get-ChildItem and use Where-Object to filter.
$fileNames = Get-ChildItem | Select-Object -ExpandProperty FullName
#then filter
$fileNames | Where-Object {$_.EndsWith("HELLO.PDF")}
#or use the aliases if you want to do less typing:
$fileNames = gci | select -exp FullName
$fileNames | ? {$_.EndsWith("HELLO.PDF")}
Just wanted to show more options -especially the Where-Object cmdlet which comes in useful when you're calling cmdlets that don't have parameters to filter.
Side note:
You may be asking what -ExpandProperty does.
If you just call gci | select -exp FullName, you will get back an array of PSCustomObjects (each of them with one property called FullName).
This can be confusing for people who don't really see that the objects are typed as it is not visible just by looking at the PowerShell script.