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DuplicateHandle info  Overview  Group

The DuplicateHandle function duplicates an object handle.

BOOL DuplicateHandle(

    HANDLE hSourceProcessHandle,

// handle to process with handle to duplicate

    HANDLE hSourceHandle,

// handle to duplicate

    HANDLE hTargetProcessHandle,

// handle to process to duplicate to

    LPHANDLE lpTargetHandle,

// pointer to duplicate handle

    DWORD dwDesiredAccess,

// access for duplicate handle

    BOOL bInheritHandle,

// handle inheritance flag

    DWORD dwOptions 

// optional actions

   );

Parameters

hSourceProcessHandle
Identifies the process containing the handle to duplicate.

Windows NT: The handle must have PROCESS_DUP_HANDLE access. For more information, see Process Objects.

hSourceHandle
Identifies the handle to duplicate. This is an open object handle that is valid in the context of the source process. For a list of objects whose handles can be duplicated, see the following Remarks section.
hTargetProcessHandle
Identifies the process that is to receive the duplicated handle. The handle must have PROCESS_DUP_HANDLE access.
lpTargetHandle
Points to a variable receiving the value of the duplicate handle. This handle value is valid in the context of the target process. If lpTargetHandle is NULL, the function duplicates the handle, but does not return the duplicate handle value to the caller.
dwDesiredAccess
Specifies the access requested for the new handle. This parameter is ignored if the dwOptions parameter specifies the DUPLICATE_SAME_ACCESS flag. Otherwise, the flags that can be specified depend on the type of object whose handle is being duplicated. For the flags that can be specified for each object type, see the following Remarks section. Note that the new handle can have more access than the original handle.
bInheritHandle
Indicates whether the handle is inheritable. If TRUE, the duplicate handle can be inherited by new processes created by the target process. If FALSE, the new handle cannot be inherited.
dwOptions
Specifies optional actions. This parameter can be zero, or any combination of the following flags:

Value

Meaning

DUPLICATE_CLOSE_SOURCE

Closes the source handle. This occurs regardless of any error status returned.

DUPLICATE_SAME_ACCESS

Ignores the dwDesiredAccess parameter. The duplicate handle has the same access as the source handle.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

DuplicateHandle can be called by either the source process or the target process. It can also be invoked where the source and target process are the same. For example, a process can use DuplicateHandle to create a noninheritable duplicate of an inheritable handle, or a handle with different access than the original handle.

The duplicating process uses the GetCurrentProcess function to get a handle of itself. To get the other process handle, it may be necessary to use some form of interprocess communication (for example, named pipe or shared memory) to communicate the process identifier to the duplicating process. This identifier is then used in the OpenProcess function to open a handle.

If the process that calls DuplicateHandle is not the target process, the duplicating process must use interprocess communication to pass the value of the duplicate handle to the target process.

The duplicate handle is the same object handle as the source handle. This means that the state of the object is the same for both handles. For example, the current file mark for a file handle is always the same for both handles.

DuplicateHandle can duplicate handles to the following types of objects:

Object

Description

Console input

The handle is returned by the CreateFile function when CONIN$ is specified, or by the GetStdHandle function when STD_INPUT_HANDLE is specified. Console handles can be duplicated for use only in the same process.

Console screen buffer

The handle is returned by the CreateFile function when CONOUT$ is specified, or by the GetStdHandle function when STD_OUTPUT_HANDLE is specified. Console handles can be duplicated for use only in the same process.

Event

The handle is returned by the CreateEvent or OpenEvent function.

File or communications device

The handle is returned by the CreateFile function.

File mapping

The handle is returned by the CreateFileMapping function.

Mutex

The handle is returned by the CreateMutex or OpenMutex function.

Pipe

A named pipe handle is returned by the CreateNamedPipe or CreateFile function. An anonymous pipe handle is returned by the CreatePipe function.

Process

The handle is returned by the CreateProcess, GetCurrentProcess, or OpenProcess function.

Registry key

Windows NT: The handle is returned by the RegCreateKey, RegCreateKeyEx, RegOpenKey, or RegOpenKeyEx function. Note that registry key handles returned by the RegConnectRegistry function cannot be used in a call to DuplicateHandle.

Windows 95: You cannot use DuplicateHandle to duplicate registry key handles.

Semaphore

The handle is returned by the CreateSemaphore or OpenSemaphore function.

Thread

The handle is returned by the CreateProcess, CreateThread, CreateRemoteThread, or GetCurrentThread function

Timer

The handle is returned by the CreateWaitableTimer or OpenWaitableTimer function.

In addition to STANDARD_RIGHTS_REQUIRED, the following access flags can be specified in the dwDesiredAccess parameter for the different object types. Note that the new handle can have more access than the original handle. However, in some cases DuplicateHandle cannot create a duplicate handle with more access permission than the original handle. For example, a file handle created with GENERIC_READ access cannot be duplicated so that it has both GENERIC_READ and GENERIC_WRITE access.

Any combination of the following access flags is valid for handles to communications devices, console input, console screen buffers, files, and pipes:

Access

Description

GENERIC_READ

Enables read access.

GENERIC_WRITE

Enables write access.

Any combination of the following access flags is valid for file-mapping objects:

Access

Description

FILE_MAP_ALL_ACCESS

Specifies all possible access flags for the file-mapping object.

FILE_MAP_READ

Enables mapping the object into memory that permits read access.

FILE_MAP_WRITE

Enables mapping the object into memory that permits write access. For write access, PAGE_READWRITE protection must have been specified when the file-mapping object was created by the CreateFileMapping function.

Any combination of the following access flags is valid for mutex objects:

Access

Description

MUTEX_ALL_ACCESS

Specifies all possible access flags for the mutex object.

SYNCHRONIZE

Windows NT only: Enables use of the mutex handle in any of the wait functions to acquire ownership of the mutex, or in the ReleaseMutex function to release ownership.

Any combination of the following access flags is valid for semaphore objects:

Access

Description

SEMAPHORE_ALL_ACCESS

Specifies all possible access flags for the semaphore object.

SEMAPHORE_MODIFY_STATE

Enables use of the semaphore handle in the ReleaseSemaphore function to modify the semaphoreís count.

SYNCHRONIZE

Windows NT only: Enables use of the semaphore handle in any of the wait functions to wait for the semaphoreís state to be signaled.

Any combination of the following access flags is valid for event objects:

Access

Description

EVENT_ALL_ACCESS

Specifies all possible access flags for the event object.

EVENT_MODIFY_STATE

Enables use of the event handle in the SetEvent and ResetEvent functions to modify the eventís state.

SYNCHRONIZE

Windows NT only: Enables use of the event handle in any of the wait functions to wait for the eventís state to be signaled.

Any combination of the following access flags is valid for handles to registry keys:

Value

Meaning

KEY_ALL_ACCESS

Specifies all possible flags for the registry key.

KEY_CREATE_LINK

Enables using the handle to create a link to a registry-key object.

KEY_CREATE_SUB_KEY

Enables using the handle to create a subkey of a registry-key object.

KEY_ENUMERATE_SUB_KEYS

Enables using the handle to enumerate the subkeys of a registry-key object.

KEY_EXECUTE

Equivalent to KEY_READ.

KEY_NOTIFY

Enables using the handle to request change notifications for a registry key or for subkeys of a registry key.

KEY_QUERY_VALUE

Enables using the handle to query a value of a registry-key object.

KEY_READ

Combines the STANDARD_RIGHTS_READ, KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, and KEY_NOTIFY values.

KEY_SET_VALUE

Enables using the handle to create or set a value of a registry-key object.

KEY_WRITE

Combines the STANDARD_RIGHTS_WRITE, KEY_SET_VALUE, and KEY_CREATE_SUB_KEY values.

Any combination of the following access flags is valid for process objects:

Access

Description

PROCESS_ALL_ACCESS

Specifies all possible access flags for the process object.

PROCESS_CREATE_PROCESS

Used internally.

PROCESS_CREATE_THREAD

Enables using the process handle in the CreateRemoteThread function to create a thread in the process.

PROCESS_DUP_HANDLE

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

PROCESS_QUERY_INFORMATION

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

PROCESS_SET_INFORMATION

Enables using the process handle in the SetPriorityClass function to set the processís priority class.

PROCESS_TERMINATE

Enables using the process handle in the TerminateProcess function to terminate the process.

PROCESS_VM_OPERATION

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

PROCESS_VM_READ

Enables using the process handle in the ReadProcessMemory function to read from the virtual memory of the process.

PROCESS_VM_WRITE

Enables using the process handle in the WriteProcessMemory function to write to the virtual memory of the process.

SYNCHRONIZE

Windows NT only: Enables using the process handle in any of the wait functions to wait for the process to terminate.

Any combination of the following access flags is valid for thread objects:

Access

Description

SYNCHRONIZE

Windows NT only: Enables using the thread handle in any of the wait functions to wait for the thread to terminate.

THREAD_ALL_ACCESS

Specifies all possible access flags for the thread object.

THREAD_DIRECT_IMPERSONATION

Used internally.

THREAD_GET_CONTEXT

Enables using the thread handle in the GetThreadContext function to read the threadís context.

THREAD_IMPERSONATE

Used internally.

THREAD_QUERY_INFORMATION

Enables using the thread handle in the GetExitCodeThread, GetThreadPriority, and GetThreadSelectorEntry functions to read information from the thread object.

THREAD_SET_CONTEXT

Enables using the thread handle in the SetThreadContext function to set the threadís context.

THREAD_SET_INFORMATION

Enables using the thread handle in the SetThreadPriority function to set the threadís priority.

THREAD_SET_THREAD_TOKEN

Used internally.

THREAD_SUSPEND_RESUME

Enables using the thread handle in the SuspendThread or ResumeThread functions to suspend or resume a thread.

THREAD_TERMINATE

Enables using the thread handle in the TerminateThread function to terminate the thread.

See Also

CloseHandle, CreateEvent, CreateFile, CreateFileMapping, CreateMutex, CreateNamedPipe, CreatePipe, CreateProcess, CreateRemoteThread, CreateSemaphore, CreateThread, CreateWaitableTimer, GetCurrentProcess, GetExitCodeProcess, GetExitCodeThread, GetPriorityClass, GetStdHandle, GetThreadContext, GetThreadPriority, GetThreadSelectorEntry, OpenEvent, OpenMutex, OpenProcess, OpenSemaphore, OpenWaitableTimer, ReadProcessMemory, RegConnectRegistry, RegCreateKey, RegCreateKeyEx, RegOpenKey, RegOpenKeyEx, ReleaseMutex, ReleaseSemaphore, ResetEvent, ResumeThread, SetEvent, SetPriorityClass, SetThreadContext, SetThreadPriority, SuspendThread, TerminateProcess, TerminateThread, VirtualProtectEx, WriteProcessMemory

See also:


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