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Running a Program from the Command Line Based on an Event

  • Artikel

The CommandLineEventConsumer class runs a specified executable program from a command line when a specified event occurs. This class is a standard event consumer that WMI provides.

When you use CommandLineEventConsumer, you should secure the executable that you want to start. If the executable is not in a secure location or not secured with a strong access control list (ACL), a user without access privileges can replace your executable with a different executable. You can use the Win32_LogicalFileSecuritySetting or Win32_LogicalShareSecuritySetting classes to change programmatically the security of a file or share. For more information, see Creating a Security Descriptor for a New Object in C++.

The basic procedure to use standard consumers is always the same, and is located in Monitoring and Responding to Events with Standard Consumers. The following procedure adds to the basic procedure, is specific to the CommandLineEventConsumer class, and describes how to create an event consumer that runs a program.

Caution

The CommandLineEventConsumer class has special security constraints. This standard consumer must be configured by a local member of the Administrators group on the local computer. If you use a domain account to create the subscription, the LocalSystem account must have the necessary permissions on the domain to verify that the creator is a member of the local Administrators group.

CommandLineEventConsumer cannot be used to start a process that runs interactively.

 

The following procedure describes how to create an event consumer that runs a process from a command line.

To create an event consumer that runs a process from a command line

  1. In the Managed Object Format (MOF) file, create an instance of CommandLineEventConsumer to receive the events you request in the query. For more information, see Designing Managed Object Format (MOF) Classes.
  2. Create an instance of __EventFilter and give it a name.
  3. Create a query to specify the type of event. For more information, see Querying with WQL.
  4. Create an instance of __FilterToConsumerBinding to associate the filter with the instance of CommandLineEventConsumer.
  5. Compile your MOF file by using Mofcomp.exe.

Example

The following code example creates a new class called "MyCmdLineConsumer" to generate events when an instance of the new class is created at the end of a MOF. The example is in MOF code, but you can create the instances programmatically by using the Scripting API for WMI or the COM API for WMI.

The following procedure describes how to create a new class called MyCmdLineConsumer.

To create a new class called MyCmdLineConsumer

  1. Create the c:\cmdline_test.bat file with a command that executes a visible program, such as "calc.exe" .
  2. Copy the MOF to a text file and save it with a .mof extension.
  3. In a Command window, compile the MOF file by using the following command: Mofcomp filename.mof.

Note

The program specified in cmdline_test.bat should execute.

 

// Set the namespace as root\subscription.
// The CommandLineEventConsumer is already compiled
// in the root\subscription namespace. 
#pragma namespace ("\\\\.\\Root\\subscription")

class MyCmdLineConsumer
{
 [key]string Name;
};

// Create an instance of the command line consumer
// and give it the alias $CMDLINECONSUMER

instance of CommandLineEventConsumer as $CMDLINECONSUMER
{
 Name = "CmdLineConsumer_Example";
 CommandLineTemplate = "c:\\cmdline_test.bat";
 RunInteractively = True;
 WorkingDirectory = "c:\\";
};    

// Create an instance of the event filter
// and give it the alias $CMDLINEFILTER
// The filter queries for instance creation event
// for instances of the MyCmdLineConsumer class

instance of __EventFilter as $CMDLINEFILTER
{
    Name = "CmdLineFilter";
    Query = "SELECT * FROM __InstanceCreationEvent"
        " WHERE TargetInstance.__class = \"MyCmdLineConsumer\"";
    QueryLanguage = "WQL";
};

// Create an instance of the binding
// between filter and consumer instances.

instance of __FilterToConsumerBinding
{
     Consumer = $CMDLINECONSUMER;
     Filter = $CMDLINEFILTER;
};

// Create an instance of this class right now. 
// The commands in c:\\cmdline_test.bat execute
// as the result of creating the instance
// of MyCmdLineConsumer.
 
instance of MyCmdLineConsumer
{
     Name = "CmdLineEventConsumer test";
};

Monitoring and Responding to Events with Standard Consumers