18. PowerShell -- Start-Job, Get-Job, Remove-Job 等

·         PowerShell Job Overview

    This topic explains how to run background jobs in Windows PowerShell on a

    local computer. For information about running background jobs on remote

    computers, see about_Remote_Jobs.

    When you start a background job, the command prompt returns immediately,

    even if the job takes an extended time to complete. You can continue to

    work in the session without interruption while the job runs.

·         PowerShell Job CMDLETS

Start-Job:

Starts a background job on a local computer.

Get-Job:

Gets the background jobs that were started in the current session.

Receive-Job:

Gets the results of background jobs.

Stop-Job:

Stops a background job.

Wait-Job:

Suppresses the command prompt until one or all jobs are                  complete.

Remove-Job:

Deletes a background job.

Invoke-Command:

The AsJob parameter runs any command as a background job on a

Remote computer. You can also use Invoke-Command to run

Any job command remotely, including a Start-Job command.

•  PowerShell Job 实例

o    实例一：  Start-Job -ScriptBlock {Get-Process}

        $job = Start-Job -ScriptBlock {Get-Process}

The above command starts a background job that runs a Get-Process    command on the local computer.

o    实例二：   PS C:\>Get-Job

        Id  Name  PSJobTypeName State      HasMoreData  Location   Command

        --  ----  ------------- -----      -----------  --------   -------

        Job1  ·BackgroundJob ·Running    ·True   ·localhost  ·Get-··Process

To get object that represent the background jobs that were started in the  current session, use the Get-Job cmdlet. Without parameters, Get-Job returns all of the jobs that were started in the current session.

  The following command gets the job with ID 1 and  saves it in the $job   variable.

       $job = Get-Job -Id 1 

    The job object contains the state of the job, which indicates whether the

    job has finished. A finished job has a state of "Complete" or "Failed". A

    job might also be blocked or running.

o    实例三：   Receive-Job -Job $job

 1. The Receive-Job cmdlet returns the results of the job.

           Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)    Id ProcessName

           -------  ------    -----      ----- -----   ------    -- -----------

               103       4    11328       9692    56           1176 audiodg

               804      14    12228      14108   100   101.74  1740 CcmExec

               668       7     2672       6168   104    32.26   488 csrss

   ...

2. Save the results of a job in a variable.

• $results = Receive-Job -Job $job

3. Save the results of the job in a file by using the redirection   operator (>) or the Out-File cmdlet.

• Receive-Job -Job $job > results.txt

4. When Receive-Job returns results, by default, it deletes those results from   the cache where job results are stored.

        C:\PS> Receive-Job -Job $job

        Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName

        -------  ------    -----      ----- -----   ------     -- -----------

            103       4    11328       9692    56            1176 audiodg

            804      14    12228      14108   100   101.74   1740 CcmExec

5. To prevent Receive-Job from deleting the job results that it has returned, use the Keep parameter.

        C:\PS> Receive-Job -Job $job -Keep

        Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName

        -------  ------    -----      ----- -----   ------     -- -----------

            103       4    11328       9692    56            1176 audiodg

            804      14    12228      14108   100   101.74   1740 CcmExec

        o    实例四：   Wait-Job -ID 10

    The above command uses the Wait-Job cmdlet to wait for a job with

ID 10.  

As a result, the Windows PowerShell prompt is suppressed until the job

is completed.

    You can also wait for a predetermined period of time. This command uses

    the Timeout parameter to limit the wait to 120 seconds. When the time

    expires, the command prompt returns, but the job continues to run in the

    background.

     Wait-Job -ID 10 -Timeout 120

         o    实例五：      STOPPING A JOB

        $job = Start-Job -ScriptBlock {Get-EventLog -Log System}

        $job | Stop-Job

    To stop a background job, use the Stop-Job cmdlet. The above command

    starts a job to get every entry in the System event log. It saves the job

    object in the $job variable.

    The above command stops the job. It uses a pipeline operator (|) to

    send the job in the $job variable to Stop-Job.

        o    实例六：   DELETING A JOB

    To delete a background job, use the Remove-Job cmdlet. The following

    command deletes the job in the $job variable.

        Remove-Job -Job $job

        o    实例七：   INVESTIGATING A FAILED JOB

  To find out why a job failed, use the Reason subproperty of the job object.

    The following command starts a job without the required credentials. It

    saves the job object in the $job variable.

         $job = Start-Job -ScriptBlock

               {New-Item -Path HKLM:\Software\MyCompany}

         Id   Name  PSJobTypeName State    HasMoreData  Location   Command

         --   ----  ------------- -----    -----------  --------   -------

         1    Job1  BackgroundJob Failed   False        localhost  New-Item -Path HKLM:\S...

    The following command uses the Reason property to find the error that

    caused the job to fail.

         $job.ChildJobs[0].JobStateInfo.Reason

    In this case, the job failed because the remote computer required explicit

    credentials to run the command. The value of the Reason property is:

         Connecting to remote server failed with the following error

         message : Access is denied.

        o    实例八：   Waiting  JOB

                Write-Host "Waiting job..."

                Get-Job|Wait-Job|Remove-Job

SEE ALSO

   about_Remote_Jobs

   about_Job_Details

   about_Remote

   about_PSSessions  

   Start-Job

   Get-Job

   Receive-Job

   Stop-Job

   Wait-Job

   Remove-Job

   Invoke-Command

参考：

https://technet.microsoft.com/zh-cn/library/hh847783(v=wps.620).aspx#

 https://technet.microsoft.com/en-us/library/dd347692.aspx 

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