Managing Files Over SFTP With PowerShell

How to manage files over SFTP with PowerShell

Tony Arulpiragasam, former infrastructure specialist for business applications at engineering and professional services firm WSP, emphasized that using PowerShell with the Posh-SSH module is an effective way to manage and automate SFTP file transfers. 

“PowerShell is a useful tool for SFTP file management because it allows for safe automation, interacts easily with scripts and provides the flexibility required to perform repetitive operations quickly,” Arulpiragasam explained. “IT [information technology] pros can use modules like Posh-SSH to improve procedures and boost productivity.” This method also supports safe file handling, task automation and improved workflow management.

Managing files over SFTP with PowerShell involves installing the free Posh-SSH module, setting it up, working with your files and then ending the session. We’ll explain each step in more detail below.

1.mInstalling the free Posh-SSH module

Posh-SSH is available on the PowerShell Gallery. You can install it by running the following command: 

Install-Module -Name Posh-SSH 

To confirm the module’s commands, run:

PS C:> Get-Command -Module posh-ssh -Noun *SFTP*

Once installed, you’ll gain access to the following commands:

We’ll work with many of these commands in the following sections.

Anand Damdiyal, founder and CEO of AI-driven finance solutions provider Spacewink, stressed the importance of keeping the Posh-SSH module updated. “Keep the Posh-SSH module updated, [as this] ensures you can take advantage of new functionality like improved command sets and security enhancements like bug fixes and patches so everything runs smoothly and reliably,” Damdiyal explained. 

2. Setting up the Posh-SSH module

To transfer files over SFTP, you need to establish a session with the SFTP server. This only needs to be done once. While you could create a new session for every task, this approach wouldn’t be efficient.

Instead, create a single SFTP session using the New-SFTPSession command. To simplify authentication, avoid managing certificates and instead use a username and password. The New-SFTPSession has a Credential parameter that accepts a PSCredential object. Use the Get-Credential command to prompt the user for a username and password.

$credential = Get-Credential

Once you have the username and password captured, pass them to the New-SFTPSession command along with the AcceptKey parameter. The AcceptKey parameter will automatically accept the key returned from the SFTP server, avoiding manual prompts:

$session = New-SFTPSession -ComputerName ‘MYSFTPSERVER’ -Credential $Credential -AcceptKey

Damdiyal advises using try-catch blocks when setting up SFTP sessions. “Wrap commands in try-catch blocks [to] capture potential issues, such as network interruptions or authentication failures and log them for easier debugging,” Damdiyal explained.

Arulpiragasam emphasized the importance of establishing secure connections and properly managing file paths to avoid errors. “Before deploying scripts, test them in a controlled environment to ensure reliability and avoid inadvertent data overwrites,” Arulpiragasam advised. “Always include error handling in your scripts to improve reliability and log essential actions to simplify troubleshooting.”

Arulpiragasam recommended the following approach to ensure your session setup is robust and handles unexpected issues effectively:

try {

Set-SFTPFile -SessionId $SFTPSession.SessionId -LocalFile “C:\path\file.txt” -RemotePath “/path/file.txt”

} catch {

Write-Output “File upload failed: $_”

}

Did You Know?

The Posh-SSH module allows you to carry out many different SFTP operations, like adding new files and deleting and retrieving existing ones. PowerShell's versatility doesn't stop here. It's also possible to manage Internet Information Services application pools and sync folders with PowerShell.

3. Working with files

If all goes well, you’ll be returned to the console. If so, you can now use this session with several commands. For example, if you need to download a file from the SFTP server to your local computer, you can use the Get-SFTPFile function:

$getParams = @{

    SessionId = $session.SessionId

    LocalPath = ‘C:\localfile.txt’

   RemoteFile = ‘C:\remoteFile.txt’

}

Get-SFTPFile @getParams

If you need to remove a file from the SFTP server, the Remove-SFTPItem function is just as straightforward as the Get-SFTPFile function:

Remove-SFTPItem -SessionId $session.SessionId -Path ‘C:\remoteFile.txt’

FYI

Be mindful when downloading and removing files. Double-check your file paths to ensure data integrity.

4. Ending the session

Once you’re done managing files on the SFTP server, you should disconnect and remove the session. While you could simply call Remove-SFTPSession and provide the session, it’s always better to check ahead of time to ensure the session is still active. You can verify the session’s existence using Get-SFTPSession.

First, check to see if your session exists. If it does, disconnect it and completely remove it from your session:

if ($session = Get-SFTPSession -SessionId $session.SessionId) {

    $session.Disconnect()

}

$null = Remove-SftpSession -SftpSession $session

The next time you need to perform any kind of SFTP task, check out the Posh-SSH PowerShell module.

The benefits of using PowerShell to manage files over SFTP

PowerShell is a highly adaptable and versatile tool with numerous uses. For example, you can: 

• Create a web scraping tool in PowerShell
• Build an interactive menu inside a PowerShell script 
• Manage user profiles with PowerShell

When it comes to managing files over SFTP in Windows-based systems, PowerShell offers the following key benefits:

• Automation for straightforward tasks: Integrating SFTP into PowerShell allows you to script and automate simple tasks, reducing the likelihood of manual errors and saving time. “PowerShell’s flexibility and its ability to interact with other technologies make it easier to automate repetitive tasks and securely manage IoT [Internet of Things] data,” Arulpiragasam explained.
• Accessibility for all team members: PowerShell truly shines in its ability to handle complex tasks with clear, easy-to-read code. This makes it a more accessible system for teams with varying programming skill levels, ensuring collaboration and improved productivity. 
• Enhanced file management with the Posh-SSH module: The Posh-SSH module further enhances file management efficiency by supporting a wide range of SFTP operations, such as uploading, downloading and deleting files. This makes your workflows more effective and streamlined.
• Secure file transfer automation: When you pair PowerShell with the free Posh-SSH module, you can easily automate your file transfers. Damdiyal emphasized that this approach works seamlessly with Windows, simplifying and speeding up file management. “Its scripting capabilities enable dynamic file handling, secure credential management and error logging, making it a versatile solution for businesses of all sizes,” Damdiyal explained.

Real-world examples

PowerShell is also effective in real-world commercial environments:

• IoT data transfers: Arulpiragasam’s company automated IoT data transfers using a PowerShell script and the Posh-SSH module. “The script securely connects to each IoT device, retrieves the required files and stores them locally,” Arulpiragasam explained. “Automating this process with Windows Task Scheduler reduced human labor, minimized errors and ensured timely data collection.”
• Financial services: Damdiyal has used PowerShell to automate nightly SFTP uploads, ensuring the secure and timely delivery of transaction reports. “IT teams also leverage it to create redundant backups, ensuring data safety and quick recovery during emergencies,” Damdiyal noted. “This automation reduces errors and improves efficiency, saving time for businesses.”

Best practices for managing files over SFTP with PowerShell

Our experts offered the following advice for users who want to manage files over SFTP with PowerShell: 

• Start with the basics: If you’re new to using PowerShell for SFTP, Damdiyal suggests starting with the fundamentals. “Learn the fundamentals of PowerShell, like cmdlet syntax and script creation,” Damdiyal recommended. “Begin with simple tasks, such as uploading a file, to build confidence before tackling complex workflows.”
• Prioritize security: Damdiyal stressed the importance of protecting sensitive credentials. “Use PowerShell’s secure mechanisms, like encrypted credential storage or the Get-Credential cmdlet, to protect your login information,” Damdiyal advised. Similarly, Arulpiragasam cautioned against saving usernames and passwords directly in scripts. “Instead, use secure methods like Get-Credential or encrypted credential files,” Arulpiragasam advised. 
• Focus on testing and error handling: Damdiyal noted that testing scripts in a controlled environment to identify potential errors or issues is crucial. Similarly, Arulpiragasam emphasized the importance of small-scale testing. “Running scripts on large, production-level data without testing on a smaller scale can result in errors or data loss,” Arulpiragasam explained. “So, you should always test on smaller datasets first.”
• Implement file logging. Damdiyal stressed that logging is vital. “Incorporate logging for all file operations, whether downloading, uploading or deleting,” Damdiyal advised. “Logs help maintain an audit trail and simplify troubleshooting in case of errors.” 

Mark Fairlie contributed to this article.