I was planning to learn Powershell for some time now and this seemed like a good opportunity to learn a few basic things: we had a txt file with urls of multiple images (one per line) and needed to download them while preserving directory structure. Below is the powershell script with comments. Things that it illustrates:

• Using System.Net.WebClient
• Join-Path helper
• 2.0 error handling using try/catch

$webclient = New-Object System.Net.WebClient                        
            
$dest = "D:\temp"            
            
$errors = @()            
            
$images = (get-content $dest"\images.txt")                        
            
for ($i=0; $i -le $images.Length – 1; $i++) {            
    $url = $images[$i]                        
            
    # DownloadFile doesn't like spaces            
    $url = $url.toString().trim();            
                
    # also requires "http://" for URL            
    if ($url.indexOf("http://") -eq -1) {            
        $url = "http://" + $url            
    }            
                
    Write-Host ($i + 1) " / " $images.Length " : " $url            
                
    if ($url -ne "") {            
        # Example URL: http://www.example.com/aaaa/bbb/image.jpg            
                
        # requirement was to preserve the folder structure            
        # removing http://                        
        $str = $url.replace("http://", "")         # www.example.com/aaaa/bbb/image.jpg            
                    
        # removing domain name            
        $str = $str.substring($str.indexOf("/"))   # /aaaa/bbb/image.jpg            
        $str = $str.replace("/", "\")              # \aaa\bbb\image.jpg            
                    
        # determining folder structure by removing file name                        
        $dir = $str.substring(0, $str.lastIndexOf("\"))            # \aaaa\bbb            
                    
        # if folder doesn't exist locally, create it            
        $imageDir = Join-Path $dest $dir            
        if (!(test-path $imageDir -pathtype container)) {            
            # md create full folder strucutre if provided.             
            # Example: D:\A\B\C\D will create all subfolders            
            md $imageDir            
        }            
                    
        $localImagePath = Join-Path $dest $str            
        Write-Host $localImagePath            
                    
        #http://stackoverflow.com/questions/2182666/powershell-2-0-try-catch-how-to-access-the-exception            
        try {            
            $webclient.DownloadFile($url, $localImagePath)            
        }             
        catch [Exception] {            
            $errors += $url            
            Write-Host "ERROR: " + $_.Exception.ToString() -foregroundcolor "red"            
        }            
    }                        
}                        
Write-Host "done. errors: "            
$errors