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

Syntax

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

Parameters

filenum
The file number used to Open the file.
record
The record (Random files) or byte position (Binary files) to lock. If omitted, the entire file is locked.
start
The first record (Random files) or byte position (Binary files) to lock from. If omitted, the current record/byte position (Seek(filenum)) is used.
end
The last record (Random files) or byte position (Binary files) to lock to.

Description

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.

Example

'' 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)
Next
Unlock #f, 1 To 100
Close #f


Differences from QB

  • None

See also