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

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　　·         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

　　>　　--  ----  ------------- -----      -----------  --------   -------
　　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>　　$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)   >　　-------  ------    -----      ----- -----   ------    -- -----------
　　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)    >　　-------  ------    -----      ----- -----   ------     -- -----------
　　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)    >　　-------  ------    -----      ----- -----   ------     -- -----------
　　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}

　　>　　--   ----  ------------- -----    -----------  --------   -------
　　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