Month of Lunches - Day 12

So everybody wants to be more efficient with their work as well as at home. This chapter should help me solve at least half of that problem. This chapter covers multitasking and background jobs in PowerShell.

Normally with PowerShell you type a command and hit return, then you sit and wait for the command to finish. You cannot run another job until the first one completes. Now you could run a second window but what happens if you have specific modules loaded or have set variables for the task your completing. Or you could run the same command and have it moved to the background. The benefit of running a command as a job is that if it will be running for a while it will allow you to continue to use the shell and store the results for later.

There are some pitfalls that deal with having commands run in the background however. If it is in the background and prompts you for input then that job will not complete and stop eventually because you cannot reply. Running a command in the shell produces error messages for you to see, but background errors will not be visible until the job is retrieved. If the job is run in the shell you will see the display as soon as the command completes, however background jobs will have to be retrieved. And last but certainly not least remember this is not real time data but a snapshot of what was going on at the exact moment the job ran.

There are a couple kinds of background jobs discussed in this chapter. The first of which is a Local Job. A local job runs for the most part, as the title states, on your local workstation. It can request information from the remote PC's if necessary through the cmdlets, but allows your terminal to do the heavy lifting. The cmdlet for this is Start-Job. This cmdlet has a lot of really useful parameters so please read the help file for full details. The following is an example that will start a background job named Local_Process to Get-Process.

                Start-Job -scriptblock {get-service} -name 'Local_Process"

Some cmdlets have the ability to be run as jobs due to parameters. One of the major ones that Don lists is Get-WmiObject. There are others and If you want to see them do help * -parameter asjob.  You may also run jobs in the remoting tools we covered in Chapter 10. The cmdlet to do this is Invoke-Command.

To check the status of running or completed jobs type

                Get-Job

This will display the list of jobs in your current session only however. No previous jobs are cached. Note that when you do this that it displays an ID number, Name, State of the job, and HASMOREDATA column. This column shows if there is data to be retrieved for that job (PowerShell removes the data once the job is retrieved). To retrieve the results of the job you run Receive-Job. With this cmdlet you can bring up the table or list you created in your scriptblock, pipe it to the Format-List or Format-Table for custom formatting, or output it in any other way you like. It’s the same as any regular PowerShell object.

There are many ways to do background jobs, and as with anything in PowerShell, no two people do things alike. Just remember that if your getting your results it's not wrong.