.net - Delete files older than X days from FTP server with PowerShell or batch file

Question

I have to write a script which accesses an FTP server, and then deletes all *.zip files which are older than X days.

As clarification: The script can't run on the FTP server.

This is what I have so far:

$ftpServer = "RandomFTPServer"
$ftpUser = "Username"
$ftpPassword = Read-Host "Password" -AsSecureString

$credentials = New-ObjectSystem.Net.NetworkCredential($ftpUser, $ftpPassword)

function Get-FtpRequest($ftpPath) {
    $ftpRequest = [System.Net.FtpWebRequest]::Create("$ftpServer/$ftpPath")
    $ftpRequest.Credentials = $credentials
    $ftpRequest.UseBinary = $true 
    $ftpRequest.KeepAlive = $true
    $ftpRequest.UsePassive = $true
    return $ftpRequest
}

Any tips on what I need to do next?

Answer 1

You have to retrieve timestamps of remote files to select the old ones.

Unfortunately, there's no really reliable and efficient way to retrieve timestamps using features offered by .NET framework/PowerShell as it does not support FTP MLSD command.

So either you use:

• ListDirectoryDetails method (FTP LIST command) to retrieve details of all files in a directory and then you deal with FTP server specific format of the details (*nix format similar to ls *nix command is the most common, drawback is that the format may change over time, as for newer files "May 8 17:48" format is used and for older files "Oct 18 2009" format is used)
• GetDateTimestamp method (FTP MDTM command) to individually retrieve timestamps for each file. Advantage is that the response is standardized by RFC 3659 to YYYYMMDDHHMMSS[.sss]. Disadvantage is that you have to send a separate request for each file, what can be quite inefficient.

Some references:

• C# class to parse WebRequestMethods.Ftp.ListDirectoryDetails FTP response
• Parsing FtpWebRequest ListDirectoryDetails line
• Retrieving creation date of file (FTP)
• PowerShell FTP download files and subfolders
• C# Download all files and subdirectories through FTP

Though Microsoft does not recommend FtpWebRequest for a new development anyway.

---

Alternatively you can use a 3rd party FTP client implementation that supports the modern MLSD command and/or has built-in support for parsing different formats of the LIST command.

For example, WinSCP .NET assembly supports both.

# Load WinSCP .NET assembly
Add-Type -Path "WinSCPnet.dll"

# Setup session options
$sessionOptions = New-Object WinSCP.SessionOptions -Property @{
    Protocol = [WinSCP.Protocol]::Ftp
    HostName = "ftp.example.com"
    UserName = "username"
    Password = "password"
}

try
{
    # Connect
    $session = New-Object WinSCP.Session
    $session.Open($sessionOptions)

    # List files
    $remotePath = "/remote/path"
    $directoryInfo = $session.ListDirectory($remotePath)

    # Find old files
    $limit = (Get-Date).AddDays(-15)

    $oldFiles =
        $directoryInfo.Files |
        Where-Object { -Not $_.IsDirectory } | 
        Where-Object { $_.LastWriteTime -lt $limit }

    # Delete them
    foreach ($oldFileInfo in $oldFiles)
    {
        $session.RemoveFile($oldFileInfo.FullName).Check()
    } 

    Write-Host "Done"
}
finally
{
    # Disconnect, clean up
    $session.Dispose()
}

---

If you can do with a plain batch file, it's actually even easier with WinSCP scripting:

winscp.com /ini=nul /log=delete.log /command ^
    "open ftp://username:password@ftp.example.com/" ^
    "rm /remote/path/*<15D" ^
    "exit"

See file masks with time constraints.

(I'm the author of WinSCP)

---

Note that WinSCP does not require any installation. So you can just have its binaries copied around with your batch file or PowerShell script.