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UnlockFile info  Overview  Group

The UnlockFile function unlocks a region in an open file. Unlocking a region enables other processes to access the region.

BOOL UnlockFile(

    HANDLE hFile,

// handle of file to unlock

    DWORD dwFileOffsetLow,

// low-order word of lock region offset

    DWORD dwFileOffsetHigh,

// high-order word of lock region offset

    DWORD nNumberOfBytesToUnlockLow,

// low-order word of length to unlock

    DWORD nNumberOfBytesToUnlockHigh 

// high-order word of length to unlock



Identifies a file that contains a region locked with LockFile. The file handle must have been created with either GENERIC_READ or GENERIC_WRITE access to the file.
Specifies the low-order word of the starting byte offset in the file where the locked region begins.
Specifies the high-order word of the starting byte offset in the file where the locked region begins.
Specifies the low-order word of the length of the byte range to be unlocked.
Specifies the high-order word of the length of the byte range to be unlocked.

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.


Unlocking a region of a file releases a lock on the file. The region to unlock must correspond exactly to an existing locked region. For example, two adjacent regions of a file cannot be locked separately and then unlocked as a single region that spans both locked regions.

A process should not be terminated with a portion of a file locked and a file that has locked regions should not be closed.

This function works on a file allocation table (FAT) - based file system only if the operating system is running SHARE.EXE.

See Also

CreateFile, LockFile

See also:

file: /Techref/os/win/api/win32/func/src/f89_9.htm, 3KB, , updated: 2000/4/7 12:19, local time: 2022/5/17 08:08,

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