HOWTO: Constants in OpenProcess API dsDesiredAccess Parameter

ID: Q172273

The information in this article applies to:

Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 5.0
Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 4.0

SUMMARY

The API text viewer included with Visual Basic 4.0 does not define the constants used in the OpenProcess API. The OpenProcess API is used to get a handle to a running process from a process ID. The existing samples in the Microsoft Knowledge Base define one of the possible constants, SYNCHRONIZE, but the other values may be of use in special situations.

MORE INFORMATION

The constants are:


PROCESS_ALL_ACCESS   =&H1F0FFF Specifies all possible access flags for
            the process object.

PROCESS_CREATE_THREAD   =&H2  Enables using the process handle in the
            CreateRemoteThread function to create a thread in the process.

PROCESS_DUP_HANDLE   =&H40 Enables using the process handle as either
            the source or target process in the DuplicateHandle function to
            duplicate a handle.

PROCESS_QUERY_INFORMATION =&H400 Enables using the process handle in the
            GetExitCodeProcess and GetPriorityClass functions to read
            information from the process object.

PROCESS_SET_INFORMATION =&H200   Enables using the process handle in the
            SetPriorityClass function to set the priority class of the
            process.

PROCESS_TERMINATE =&H1  Enables using the process handle in the
            TerminateProcess function to terminate the process.

PROCESS_VM_OPERATION =&H8  Enables using the process handle in the
            VirtualProtectEx and WriteProcessMemory functions to modify the
            virtual memory of the process.

PROCESS_VM_READ      =&H10 Enables using the process handle in the
            ReadProcessMemory function to read from the virtual memory of
            the process.

PROCESS_VM_WRITE  =&H20 Enables using the process handle in the
            WriteProcessMemory function to write to the virtual memory of
            the process.

SYNCHRONIZE    =&H100000 Enables using the process handle in any of the
            wait functions to wait for the process to terminate.

If you need to create a handle that is to be used for more than one type of access, you should add the desired access type parameters together. For example, to get a handle to use with WaitForSingleObject and GetExitCodeProcess, you would use:


   hProcess = OpenProcess(PROCESS_QUERY_INFORMATION+SYNCHRONIZE,FALSE,pid)

REFERENCES

For additional information, please see the following article(s) in the Microsoft Knowledge Base:

Q129797 : HOWTO: Launch a Win32 Application from Visual Basic

Q150767 : HOWTO: Redirect Standard I/O of a Console Application

Keywords : kbGrpVBDB
Version : WINDOWS:4.0, 5.0
Platform : WINDOWS
Issue type : kbhowto