Restricts read/write access to a file or portion of a file

Lock #filenum, record
Lock #filenum, start To end

The file number used to Open the file.
The record (Random files) to lock.
The first byte position (Binary files) to lock from.
The last byte position (Binary files) to lock to.

Lock temporarily restricts access by other threads or programs to a file, or portion of a file, usually to allow safe writing to it.

After modifying the data, an Unlock with the same parameters as the Lock should be issued.

Note: This command does not always work, neither as documented nor as expected. It appears to be broken at the moment.

'' e.g. locking a file, reading 100 bytes, and unlocking it.
'' To run, make sure there exists a file called 'file.ext'
'' in the current directory that is at least 100 bytes.

Dim array(1 To 100) As Integer
Dim f As Integer, i As Integer
f = FreeFile
Open "file.ext" For Binary As #f
Lock #f, 1 To 100
For i = 1 To 100
    Get #f, i, array(i)
Unlock #f, 1 To 100
Close #f

Differences from QB:
See also:
Back to File I/O Functions

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