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StopProcessSample03 Sample

 

This sample shows how to write a cmdlet whose parameters have aliases and whose parameters support wildcard characters. This cmdlet is similar to the Stop-Process cmdlet provided by Windows PowerShell 2.0.

How to build the sample by using Visual Studio.

  1. With the Windows PowerShell 2.0 SDK installed, navigate to the StopProcessSample03 folder. The default location is C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0\Samples\sysmgmt\WindowsPowerShell\csharp\StopProcessSample03.

  2. Double-click the icon for the solution (.sln) file. This opens the sample project in Microsoft 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/StopProcessSample03

  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 stopprossessample03

  5. Run the following command to run the cmdlet:

    stop-proc

Requirements

This sample requires Windows PowerShell 2.0.

Demonstrates

This sample demonstrates the following.

  • Declaring a cmdlet class by using the Cmdlet attribute.

  • Declaring a cmdlet parameters by using the Parameter attribute.

  • Adding aliases to parameter declarations..

  • Adding wildcard support to parameters.

Example

This sample shows how to declare parameter aliases and support wildcards.

using System;
using System.Diagnostics;
using System.Collections;
using Win32Exception = System.ComponentModel.Win32Exception;
using System.Management.Automation;             //Windows PowerShell namespace
using System.Globalization;

namespace Microsoft.Samples.PowerShell.Commands
{

   #region StopProcCommand

    /// <summary>
   /// This class implements the stop-proc cmdlet.
   /// </summary>
   [Cmdlet(VerbsLifecycle.Stop, "Proc",
       SupportsShouldProcess = true)]
   public class StopProcCommand : Cmdlet
   {
       #region Parameters

      /// <summary>
      /// This parameter provides the list of process names on 
      /// which the Stop-Proc cmdlet will work.
      /// </summary>
       [Parameter(
          Position = 0,
          Mandatory = true,
          ValueFromPipeline = true,
          ValueFromPipelineByPropertyName = true,
          HelpMessage = "The name of one or more processes to stop. Wildcards are permitted."
       )]
       [Alias("ProcessName")]
       public string[] Name
       {
           get { return processNames; }
           set { processNames = value; }
       }
       private string[] processNames;

       /// <summary>
       /// This parameter overrides the ShouldContinue call to force 
       /// the cmdlet to stop its operation. This parameter should always 
       /// be used with caution.
       /// </summary>
       [Parameter]
       public SwitchParameter Force
       {
          get { return force; }
          set { force = value; }
       }
       private bool force;

       /// <summary>
       /// This parameter indicates that the cmdlet should return 
       /// an object to the pipeline after the processing has been 
       /// completed.
       /// </summary>
       [Parameter(
          ValueFromPipelineByPropertyName = true,
          HelpMessage = "If set, the process(es) will be passed to the pipeline after stopped."
       )]
       public SwitchParameter PassThru
       {
          get { return passThru; }
          set { passThru = value; }
       }
       private bool passThru;

       #endregion Parameters

       #region Cmdlet Overrides
       /// <summary>
       /// The ProcessRecord method does the following for each of the 
       /// requested process names:
       /// 1) Check that the process is not a critical process.
       /// 2) Attempt to stop that process.
       /// If no process is requested then nothing occurs.
       /// </summary>   
       protected override void ProcessRecord()
       {   
           Process[] processes = null;

           try 
           { 
               processes = Process.GetProcesses(); 
           }
           catch (InvalidOperationException ioe)
           {
               base.ThrowTerminatingError(new ErrorRecord(ioe,
                         "UnableToAcessProcessList",
                             ErrorCategory.InvalidOperation,
                                 null));
           }


           // For every process name passed to the cmdlet, get the associated 
           // processes.  
           // Write a nonterminating error for failure to retrieve 
           // a process.
           foreach (string name in processNames)
           {
               // Write a user-friendly verbose message to the pipeline. These 
               // messages are intended to give the user detailed information 
               // on the operations performed by the cmdlet. These messages will
               // appear with the -Verbose option.
               string message = String.Format(CultureInfo.CurrentCulture, 
                                    "Attempting to stop process \"{0}\".", name);
               WriteVerbose(message);

               // Validate the process name against a wildcard pattern.  
               // If the name does not contain any wildcard patterns, it 
               // will be treated as an exact match.
               WildcardOptions options = WildcardOptions.IgnoreCase | 
                                         WildcardOptions.Compiled;
               WildcardPattern wildcard = new WildcardPattern(name,options);           

               foreach (Process process in processes)
               {
                   string processName;

                   try
                   {
                       processName = process.ProcessName;
                   }
                   catch (Win32Exception e)
                   {
                       WriteError(new ErrorRecord(
                                              e, "ProcessNameNotFound",
                                                ErrorCategory.ObjectNotFound,
                                                  process)
                                 );
                       continue;
                   }

                   // Write a debug message to the host that can be used when 
                   // troubleshooting a problem. All debug messages will appear 
                   // with the -Debug option.
                   message = String.Format(CultureInfo.CurrentCulture, 
                                "Acquired name for pid {0} : \"{1}\"",
                                      process.Id, processName);
                   WriteDebug(message);

                   // Check to see if this process matches the current process 
                   // name pattern. Skip this process if it does not.
                   if (!wildcard.IsMatch(processName))
                   {
                       continue;
                   } 

                   // Stop the process.
                   SafeStopProcess(process);
               } // foreach (Process...
           } // foreach (string...
       } // ProcessRecord

       #endregion Cmdlet Overrides

       #region Helper Methods

       /// <summary>
       /// Safely stops a named process.  Used as standalone function
       /// to declutter the ProcessRecord method.
       /// </summary>
       /// <param name="process">The process to stop.</param>
       private void SafeStopProcess(Process process)
       {
           string processName = null;
           try
           {
               processName = process.ProcessName;
           }
           catch (Win32Exception e)
           {
               WriteError(new ErrorRecord(e, "ProcessNameNotFound",
                                 ErrorCategory.ObjectNotFound, process));
               return;               
           }

           string message = null;

           // Confirm the operation first.
           // This is always false if the WhatIf parametr is specified.
           if (!ShouldProcess(string.Format(CultureInfo.CurrentCulture, 
                    "{0} ({1})", processName, process.Id)))
           {
               return;
           }

           // Make sure that the user really wants to stop a critical
           // process that could possibly stop the computer.
           bool criticalProcess = criticalProcessNames.Contains(processName.ToLower(CultureInfo.CurrentCulture));

           if (criticalProcess && !force)
           {
               message = String.Format(CultureInfo.CurrentCulture, 
                            "The process \"{0}\" is a critical process and should not be stopped. Are you sure you wish to stop the process?",
                                processName);

               // It is possible that ProcessRecord is called multiple 
               // when objects are recieved as inputs from a pipeline.
               // So, to retain YesToAll and NoToAll input that the 
               // user may enter across mutilple calls to this 
               // function, they are stored as private members of the 
               // Cmdlet.
               if (!ShouldContinue(message, "Warning!",
                            ref yesToAll, ref noToAll))
               {
                   return;
               }
           } // if (criticalProcess...

           // Display a warning message if stopping a critical 
           // process.
           if (criticalProcess)
           {
               message = String.Format(CultureInfo.CurrentCulture, 
                            "Stopping the critical process \"{0}\".",
                                processName);
               WriteWarning(message);
           } // if (criticalProcess...

           try
           {
               // Stop the process.
               process.Kill();
           }
           catch (Exception e)
           {
               if ((e is Win32Exception) || (e is SystemException) ||
                   (e is InvalidOperationException))
               {
                   // This process could not be stopped so write
                   // a non-terminating error.
                   WriteError(new ErrorRecord(e, "CouldNotStopProcess",
                                    ErrorCategory.CloseError,
                                    process)
                              );
                   return;
               } // if ((e is...
               else throw;
           } // catch 

           message = String.Format(CultureInfo.CurrentCulture, 
                        "Stopped process \"{0}\", pid {1}.",
                              processName, process.Id);

           WriteVerbose(message);

           // If the PassThru parameter is specified, 
           // return the terminated process to the pipeline.
           if (passThru)
           {
               message = String.Format(CultureInfo.CurrentCulture, 
                            "Writing process \"{0}\" to pipeline",
                                processName);
               WriteDebug(message);
               WriteObject(process);
           } // if (passThru...
       } // SafeStopProcess

       #endregion Helper Methods

       #region Private Data

       private bool yesToAll, noToAll;

       /// <summary>
       /// Partial list of the critical processes that should not be 
       /// stopped.  Lower case is used for case insensitive matching.
       /// </summary>
       private ArrayList criticalProcessNames = new ArrayList(
          new string[] { "system", "winlogon", "spoolsv" }
       );

       #endregion Private Data

   } // StopProcCommand

   #endregion StopProcCommand
} // namespace Microsoft.Samples.PowerShell.Commands
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