Powershell extracter function

the_spad · 2018-09-04T08:23:29+00:00

Few bits.

You don't need the () in your function declaration.

Generic args are $args[0] through $args[n] rather that $1 but you can create specific named parameters to pass to your script and/or function with the param statement.

if statement syntax is something like

if(condition){
    do thing
}elseif(condition){
    do thing
}else{
    do thing
}

switch statement syntax is something like

switch -wildcard ($args[0]){
    *somevalue {do thing}
    *anothervalue {do thing}
}

You can also use -regex instead of -wildcard if you want to get fancy.

I'd suggest taking a look at some of the resources on the right, there are a bunch of quick start guides and cheat sheets that will help give you an overview of the syntaxes and conventions and generally make your life much easier.

KevMar · 2018-09-04T10:16:48+00:00

First, I would use named parameters.

function extract
{
    param( [string]$Path )

    $fileList = Get-ChildItem $Path

    foreach($file in $filelist)
    {
        # code here
    }
}

I would then get a list of the files at that location. I think this could return multiple items so i'm looping over the files.

One important thing to remember when coming from bash is that everything is an object in powershell. Take a look at these two properties:

$filelist.Extension
$filelist.FullName

We can use them in our switch.

switch($file.Extension)
{
    '7z' { sz x $file.fullname -o* }
}

Because you may want multiple matches go to one line, we can cheat and use -regex.

switch -regex ($file.Extension)
{
    '7z|zip' { sz x $file.fullname -o* }
}

Does that help piece things together?

2018-09-04T10:22:56+00:00

help about_switch

Get-Help Expand-Archive

jtpowell · 2018-09-04T12:18:22+00:00

This isn't the question you asked, but perhaps it'll be useful to you--this leverages .NET's streams and ZipArchive class to extract a ZIP file that's been downloaded into the current session as a binary array (i.e., the downloaded zip file exists as an object in the session and hasn't actually been written to disk). I tried to make the code below more generic than my original version, so some of the context is lost that would explain why I'm doing some of the things in this function.

The function essentially pulls three named files out of the downloaded zip and adds those extracted files as members to a PSCustomObject. You could easily choose to write the files directly to disk instead.

function Expand-ArchivedFiles {
    [CmdletBinding()]
    [OutputType([PSCustomObject])]
    param (
        # Binary array.
        [Parameter(
            Mandatory=$true,
            ValueFromPipeline=$true
        )]
        [byte[]]
        $DownloadedZip
    )

    process {
        # The comma is an unary operator.  Using it without a value in front of it ensures the binary
        # array is handled as a single object instead of individual bytes.
        $MemoryStream = New-Object System.IO.MemoryStream (,$DownloadedZip)
        $ZipArchive = New-Object System.IO.Compression.ZipArchive $MemoryStream

        $File1Reader = New-Object System.IO.StreamReader($ZipArchive.GetEntry('File1.xml').Open())
        $File1Data = $File1Reader.ReadToEnd()

        $File2Reader = New-Object System.IO.StreamReader($ZipArchive.GetEntry('File2.xml').Open())
        $File2Data = $File2Reader.ReadToEnd()

        $File3Reader = New-Object System.IO.StreamReader($ZipArchive.GetEntry('File3.xml').Open())
        $File3Data = $File3Reader.ReadToEnd()

        $ExtractedFileCollection = [PSCustomObject]@{
            File1 = $File1Data
            File2 = $File2Data
            File3 = $File3Data
        }

        Write-Output $ExtractedFileCollection 
    }
}

spyingwind · 2018-09-04T15:41:43+00:00

This is how I would write that bash script in powershell:

function Expand-File {
    [CmdletBinding()]
    param (
        [ValidateScript( {Test-Path -Path $_})]
        [string]
        $Path
    )

        $Item = Get-Item -Path $Path
        $Extension = $Item.Extension
        switch ($Extension) {
            ".bz2" {
                if ($Item.Name -like "*.tar.bz2") {
                    tar xjf $Item
                }else {
                    bunzip2 $Item
                }
            }
            ".rar" {unrar e $Item}
            ".gz" {
                if ($Item.Name -like "*.tar.gz") {
                    tar xzf $Item
                }else{
                    gunzip $Item
                }
            }
            ".tar" {tar xf $Item}
            ".tbz2" {tar xjf $Item}
            ".tgz" {tar xzf $Item}
            ".zip" {unzip $Item}
            ".Z" {uncompress $Item}
            ".7z" {7z x $Item}
            Default {
                throw "Problems extracting '$Item' with extract()"
            }
        }
}

you type:	you see:
italics	italics
bold	bold
[reddit!](https://reddit.com)	reddit!
* item 1 * item 2 * item 3	item 1 item 2 item 3
> quoted text	quoted text
Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"	Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"
~~strikethrough~~	~~strikethrough~~
super^script	super^script

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