WaitForSingleObject

The WaitForSingleObject function returns when one of the following occurs:

The specified object is in the signaled state.
The time-out interval elapses.

DWORD WaitForSingleObject(
  HANDLE hHandle,        // handle to object to wait for
  DWORD dwMilliseconds   // time-out interval in milliseconds
);

Parameters

hHandle: Handle to the object. For a list of the object types whose handles can be specified, see the following Remarks section.
Windows NT: The handle must have SYNCHRONIZE access. For more information, see Standard Access Rights.
dwMilliseconds: Specifies the time-out interval, in milliseconds. The function returns if the interval elapses, even if the object's state is nonsignaled. If dwMilliseconds is zero, the function tests the object's state and returns immediately. If dwMilliseconds is INFINITE, the function's time-out interval never elapses.

Return Values

If the function succeeds, the return value indicates the event that caused the function to return. This value can be one of the following.

Value	Meaning
WAIT_ABANDONED	The specified object is a mutex object that was not released by the thread that owned the mutex object before the owning thread terminated. Ownership of the mutex object is granted to the calling thread, and the mutex is set to nonsignaled.
WAIT_OBJECT_0	The state of the specified object is signaled.
WAIT_TIMEOUT	The time-out interval elapsed, and the object's state is nonsignaled.

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

Remarks

The WaitForSingleObject function checks the current state of the specified object. If the object's state is nonsignaled, the calling thread enters an efficient wait state. The thread consumes very little processor time while waiting for the object state to become signaled or the time-out interval to elapse.

Before returning, a wait function modifies the state of some types of synchronization objects. Modification occurs only for the object whose signaled state caused the function to return. For example, the count of a semaphore object is decreased by one.

The WaitForSingleObject function can wait for the following objects:

Change notification
Console input
Event
Job
Mutex
Process
Semaphore
Thread
Waitable timer

Windows CE: Windows CE does not support waiting for semaphores, change notification objects, console input, and timers.

Waiting on an invalid handle causes WaitForSingleObject to return WAIT_FAILED.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winbase.h.
  Import Library: Use kernel32.lib.