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GetProcessSample04 Sample

 

This sample shows how to implement a cmdlet that retrieves the processes on the local computer. It generates a nonterminating error if an error occurs while retrieving a process. This cmdlet is a simplified version of the Get-Process cmdlet provided by Windows PowerShell 2.0.

How to build the sample using Visual Studio.

  1. With the Windows PowerShell 2.0 SDK installed, navigate to the GetProcessSample04 folder. The default location is C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0\Samples\sysmgmt\WindowsPowerShell\csharp\GetProcessSample04.

  2. Double-click the icon for the solution (.sln) file. This opens the sample project in Visual Studio.

  3. In the Build menu, select Build Solution.

The library for the sample will be built in the default \bin or \bin\debug folders.

How to run the sample

  1. Create the following module folder:

    [user]/documents/windowspowershell/modules/GetProcessSample04

  2. Copy the sample assembly to the module folder.

  3. Start Windows PowerShell.

  4. Run the following command to load the assembly into Windows PowerShell:

    Import-module getprossessample04

  5. Run the following command to run the cmdlet:

    get-proc

Requirements

This sample requires Windows PowerShell 2.0.

Demonstrates

This sample demonstrates the following.

  • Declaring a cmdlet class using the Cmdlet attribute.

  • Declaring a cmdlet parameter using the Parameter attribute.

  • Specifying the position of the parameter.

  • Specifying that the parameter takes input from the pipeline. The input can be taken from an object or a value from a property of an object whose property name is the same as the parameter name.

  • Declaring a validation attribute for the parameter input.

  • Trapping a nonterminating error and writing an error message to the error stream.

Example

This sample shows how to create a cmdlet that handles nonterminating errors and writes error messages to the error stream.

namespace Microsoft.Samples.PowerShell.Commands
{
    using System;
    using System.Diagnostics;
    using System.Management.Automation;      // Windows PowerShell namespace.
   #region GetProcCommand

   /// <summary>
   /// This class implements the get-proc cmdlet.
   /// </summary>
   [Cmdlet(VerbsCommon.Get, "Proc")]
   public class GetProcCommand : Cmdlet
   {
      #region Parameters

       /// <summary>
       /// The names of the processes to act on.
       /// </summary>
       private string[] processNames;

      /// <summary>
      /// Gets or sets the list of process names on 
      /// which the Get-Proc cmdlet will work.
      /// </summary>
      [Parameter(
         Position = 0,
         ValueFromPipeline = true,
         ValueFromPipelineByPropertyName = true)]
      [ValidateNotNullOrEmpty]
      public string[] Name
      {
         get { return this.processNames; }
         set { this.processNames = value; }
      }

      #endregion Parameters

      #region Cmdlet Overrides

      /// <summary>
      /// The ProcessRecord method calls the Process.GetProcesses 
      /// method to retrieve the processes specified by the Name 
      /// parameter. Then, the WriteObject method writes the 
      /// associated processes to the pipeline.
      /// </summary>
      protected override void ProcessRecord()
      {        
          // If no process names are passed to cmdlet, get all 
          // processes.
          if (this.processNames == null)
          {
              WriteObject(Process.GetProcesses(), true);
          }
          else
          {
              // If process names are passed to the cmdlet, get and write 
              // the associated processes.
              // If a nonterminating error occurs while retrieving processes, 
              // call the WriteError method to send an error record to the 
              // error stream.
              foreach (string name in this.processNames)
              {
                  Process[] processes;

                  try
                  {
                      processes = Process.GetProcessesByName(name);
                  }
                  catch (InvalidOperationException ex)
                  {
                      WriteError(new ErrorRecord(
                         ex,
                         "UnableToAccessProcessByName",
                         ErrorCategory.InvalidOperation,
                         name));
                      continue;
                  }

                  WriteObject(processes, true);
              } // foreach (string name...
          } // else
      } // ProcessRecord

      #endregion Overrides
    } // End GetProcCommand class.

   #endregion GetProcCommand
}

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