LockFile

The LockFile function locks a region in an open file. Locking a region prevents other processes from accessing the region.

BOOL LockFile(
  HANDLE hFile,           // handle of file to lock
  DWORD dwFileOffsetLow,  // low-order word of lock region offset
  DWORD dwFileOffsetHigh,  // high-order word of lock region offset
  DWORD nNumberOfBytesToLockLow,
                          // low-order word of length to lock
  DWORD nNumberOfBytesToLockHigh 
                          // high-order word of length to lock
);
 

Parameters

hFile

Handle to the file with a region to be locked. The file handle must have been created with GENERIC_READ or GENERIC_WRITE access to the file (or both).

dwFileOffsetLow

Specifies the low-order word of the starting byte offset in the file where the lock should begin.

dwFileOffsetHigh

Specifies the high-order word of the starting byte offset in the file where the lock should begin.

nNumberOfBytesToLockLow

Specifies the low-order word of the length of the byte range to be locked.

nNumberOfBytesToLockHigh

Specifies the high-order word of the length of the byte range to be locked.

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

Locking a region of a file gives the locking process exclusive access to the specified region. File locks are not inherited by processes created by the locking process.

Locking a region of a file denies all other processes both read and write access to the specified region. Locking a region that goes beyond the current end-of-file position is not an error.

Locks may not overlap an existing locked region of the file.

The UnlockFile function unlocks a file region locked by LockFile.

QuickInfo

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

See Also

File I/O Overview, File Functions, CreateFile, UnlockFile