Powershell, download file in multiple threads

For developers using. NET methods and types are available for us in Powershell. To start the PowerShell script, I type. More commands can be aliased, such that Unix Developers can manage part of Windows Clients and servers and still have that familiar Unix syntax feel of it This concludes our introductory tour of Powershell.

I would like to say happy coding, but it is perhaps more correct to say happy Powershell scripting? Share this article on LinkedIn. Lagt inn av Tore Aurstad kl.

Tore Aurstad 28 March at Sondre 25 March at Tore Aurstad 25 March at Blogger 12 August at Guntahar 13 January at To get output, we need to run the EndInvoke method of PowerShell instance for each iteration and provide it the runspace handle. This has some ramifications for error handling, we either need to completely handle errors inside the worker function, or we need to append error data to our return object.

This is because each runspace runs in its own environment. However, even this can be a little tricky to understand. What would be the expected behavior if we slightly modified our worker function to this?

The initial assumption tends to be that only file1. When a cmdlet runs as a background job, the work is done asynchronously in its own thread separate from the pipeline thread that the cmdlet is using. From the user perspective, when a cmdlet runs as a background job, the command prompt returns immediately even if the job takes an extended amount of time to complete, and the user can continue without interruption while the job runs.

Powershell jobs are quite a high level construct - as such, there is limited control at the low level and limited ability to manage multiple threads and have them share variables, etc. They support parallel processing out of the box. Again, like Jobs, they are quite high level and the amount of control they give us is limited. From Technet. NET provides the System. Runspaces namespace that gives us access to a set of classes designed to create, manipulate and orchestrate a pool of Powershell processes.

This forms the basis of multi threading your Powershell scripts. I had the idea to try to directly leverage the TPL from within Powershell and effectively tackle the problem in exactly the same way as one would if writing multi threaded code in. NET, e. Background jobs and workflows didn't provide me with enough control so I quickly dismissed them.

My preference was to use the TPL but I quickly found that things didn't quite work. Although we can write. NET code directly from within Powershell, that doesn't mean we should try to follow the same patterns in both.

They are both markedly different and at the thread level I found that trying to instantiate and manipulate threads from within a Powershell script was a recipe for disaster. That left me using the System.

Runspace namespace and the results were quite pleasing. This is our first demonstration of a multi threaded Powershell script. We create 50 local text files by downloading a file from the web. Perhaps you need some PowerShell code to run every time someone logs into a computer. You can create a scheduled job for this. This scheduled job will write a line to a log file every time someone logs in. Once you run the above commands you will get an output similar to when creating a new job that will show the job ID, the scriptblock and some other attributes as shown below.

After a few login attempts, you can see from the below screenshot that it has logged the attempts. Another way to use jobs is to use the AsJob parameter that is built in to many PowerShell commands.

Since there are many different commands, you can find all of them using Get-Command as shown below. One of the most prevalent commands is Invoke-Command. Normally, when you run this command it will start executing a command immediately.

While some commands will immediately return, allowing you to continue on with what you were doing, some will wait until the command is finished. Using the AsJob parameter does exactly what it sounds like and runs the executed command as a job instead of running it synchronously in the console.

While most of the time AsJob can be used with the local machine, Invoke-Command does not have a native option to run on local machine. There is a workaround by using Localhost as the ComputerName parameter value.

Below is an example of this workaround. To show the AsJob parameter in action, the below example uses Invoke-Command to sleep for five seconds and then repeat the same command using AsJob to show the difference in execution times. Up until now, you have been learning about ways to use additional threads with PowerShell only using the built in commands.

Another option to multithread your script is to use a separate runspace. Runspaces are the enclosed area that the thread s running PowerShell operate within. While the runspace that is used with the PowerShell console is restricted to a single thread, you can use additional runspaces to allow for use of additional threads.

While a runspace and a PSJob share many similarities, there are some big differences in performance. The biggest difference in runspaces and PSjobs is the time it takes to set up and break down each one. In the example from the previous section, the PSjob created took about ms to bring up. In contrast to the PSJob creation, a runspace is created ahead of time.

The majority of the time it takes to spin up a runspace job is handled before any code has been added. Below is an example of running the same command that we used for the PSjob in the runspace instead.

By contrast, below is the code used for the runspace version. You can see there is much more code to execute the same task. Using runspaces can be a daunting task at first since there is no more PowerShell command hand-holding. You will have to deal with. NET classes directly. In this walkthrough, you are going to create a separate runspace from your PowerShell console and a separate PowerShell instance.

Then you will assign the new runspace to the new PowerShell instance and add code to that instance. The first thing you need to do is create your new runspace. You do this using the runspacefactory class. Store this to a variable, like what is shown below, so that it can be referenced later. Now that the runspace is created, assign it to a PowerShell instance to run PowerShell code. Next, add the runspace to your PowerShell instance, open the runspace to be able to run code and add your scriptblock.

This is shown below with a scriptblock to sleep for five seconds. So far, the scriptblock still has not been run. All that has been done so far is to define everything for the runspace.

To start running the scriptblock, you have two options. When using BeginInvoke , store the output to a variable as it will be required to see the status of the scriptblock in the runspace as shown below. Once you have the output from the BeginInvoke stored to a variable, you can check that variable to see the status of the job as seen below in the IsCompleted property.

Another reason you will need to store the output in a variable is because unlike the Invoke method, BeginInvoke will not automatically return the output when the code is finished. To do this, you must use the EndInvoke method once it has been completed.

How to download multiple files with powershell Ask Question. Asked 3 years, 9 months ago. Active 3 years, 9 months ago. Viewed 6k times. Files were not downloaded. Improve this question. Camilo Riviere. Camilo Riviere Camilo Riviere 51 1 1 silver badge 8 8 bronze badges.

The two overloads either require string or Uri but because you're offering an object the code isn't working. What's the actual error message? Whats the rest of the exception? Matt I've edited my question to contain the answer with an edit that you recommended. Thank you for your help. Add a comment. Active Oldest Votes.