Powershell populate array from list of files

Question

I need to populate a powershell array with the filenames of files stored in a directory based on their names. I need a different array for each set of files (see Example folder structure) to be used as part of another process.

I would like this to be automatic and create the arrays on the fly, so I would have arrays containing all the filenames starting with processor123, another for processorabc and processorxyz. The names of these arrays can be stored in another array named $arrynames. It needs to be dynamic in case a new processor is introduced, I do not want to rely on users to enter the file names.

Example folder structure;

c:\directory\processor123\processor123.log.20150604
c:\directory\processor123\processor123.log.20150603
c:\directory\processor123\processor123.log.20150602
c:\directory\processor123\processor123.log.20150601
c:\directory\processor123\processor123.log.20150531
c:\directory\processorabc.log.20150604
c:\directory\processorabc.log.20150603
c:\directory\processorabc.log.20150602
c:\directory\processorabc.log.20150601
c:\directory\processorabc.log.20150531
c:\directory\processorxyz.log.20150604
c:\directory\processorxyz.log.20150603
c:\directory\processorxyz.log.20150602
c:\directory\processorxyz.log.20150601
c:\directory\processorxyz.log.20150531

$ArryNames

processor123
processorabc
processorxyz

$processor123

c:\directory\processor123\processor123.log.20150604
c:\directory\processor123\processor123.log.20150603
c:\directory\processor123\processor123.log.20150602
c:\directory\processor123\processor123.log.20150601
c:\directory\processor123\processor123.log.20150531

$processorabc

c:\directory\processorabc.log.20150604
c:\directory\processorabc.log.20150603
c:\directory\processorabc.log.20150602
c:\directory\processorabc.log.20150601
c:\directory\processorabc.log.20150531

Ive tried a couple of things but nothing works, I'm pretty new to the scripting world — Wiggum123
– Wiggum123, Commented Jun 4, 2015 at 13:00
Even if you're "new", you should have posted some code in your question indicating that you have tried something. What you ask for is doable, although I say you'd better not go with a variable named $processorabc, as it's pretty hard to refer a variable by its name. Instead, you might want to use $sometable["processor123"]. If there would be a "processor" named ArryNames, you'll be screwed, but using a hash table will still work, you'll just get a `$sometable["ArryNames"] and no breaking of the script. — Vesper
– Vesper, Commented Jun 4, 2015 at 13:12
Ok, apologies, thanks for the heads up on hash tables, I will work on this, looks promising. — Wiggum123
– Wiggum123, Commented Jun 4, 2015 at 13:15
@Vesper Not only to indicate that he tried something, but to help the rest of us a) avoid wasting time on things he already tried and/or b) point out potential mistakes in his previous attempts. — Ansgar Wiechers
– Ansgar Wiechers, Commented Jun 4, 2015 at 13:15

Mathias R. Jessen · Accepted Answer · 2015-06-04 13:25:21Z

1

So, what you'll want to do for each string:

Extract first part of file name
Put entire string into array matching the first part

As already mentioned in comments, you can use a hashtable to hold the arrays, with the file prefix being the key:

# Set up a hashtable
$HashTable = @{}

# Pipe your list of file paths to ForEach-Object
Get-Content C:\filenames.txt |ForEach-Object {
    # Extract the filename with [System.IO.Path]::GetFileName(), split it by dots and grab only the part before the first dot
    $Prefix = [System.IO.Path]::GetFileName($_) -split "\." |Select-Object -First 1
    # Use the extracted prefix to place the string in the correct hashtable entry
    $HashTable[$Prefix] += $_
}

Now, you can reference the first 5 paths with: $HashTable["processor123"]

answered Jun 4, 2015 at 13:25

Mathias R. Jessen

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1 Comment

Wiggum123 Over a year ago

you sir are a genius, That works exactly as desired. Having never used hash tables before this is all new to me, thankyou for adding all the comments as well.

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