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UnlockFileEx info  Overview  Group

The UnlockFileEx function unlocks a previously locked byte range in an open file.

BOOL UnlockFileEx(

    HANDLE hFile,

// handle of file to unlock

    DWORD dwReserved,

// reserved, must be set to zero

    DWORD nNumberOfBytesToUnlockLow,

// low order 32-bits of length to unlock

    DWORD nNumberOfBytesToUnlockHigh,

// high order 32-bits of length to unlock

    LPOVERLAPPED lpOverlapped 

// addr. of struct. with unlock region start offset



Identifies an open handle to a file that is to have an existing locked region unlocked. The handle must have been created with either GENERIC_READ or GENERIC_WRITE access to the file.
Reserved parameter; must be zero.
Specifies the low-order 32-bits of the length of the byte range to unlock.
Specifies the high-order 32-bits of the length of the byte range to unlock.
Points to an OVERLAPPED structure that the function uses with the unlocking request. This structure contains the file offset of the beginning of the unlock range.

Return Values

If the function succeeds, the return value is nonzero.

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


Unlocking a region of a file releases a previously acquired lock on a file. The region to unlock must correspond exactly to an existing locked region. Two adjacent regions of a file can not be locked separately and then unlocked using a single region that spans both locked regions.

If a process terminates with a portion of a file locked or closes a file that has outstanding locks, the behavior is not specified.

See Also

CreateFile, LockFile, LockFileEx, OVERLAPPED, UnlockFile 

file: /Techref/os/win/api/win32/func/src/f89_10.htm, 3KB, , updated: 2000/4/7 12:19, local time: 2022/5/26 12:42,

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