Name
Lock Procedure
Class
Microsoft.VisualBasic.FileSystem
Syntax
Lock(filenumber[, record]
or:
Lock(filenumber[, fromrecord,torecord]
-
filenumber
Use: Required
Data Type: Integer
Any valid file number
-
record
Use: Optional
Data Type: Long
The record or byte number at which to commence the lock
-
fromrecord
Use: Optional
Data Type: Long
The first record or byte number to lock
-
torecord
Use: Optional
Data Type: Long
The last record or byte number to lock
Description
The Lock
procedure prevents another process from
accessing a record, section, or whole file until it is unlocked by
the Unlock
function.
Use the Lock
procedure in situations where
multiple programs or more than one instance of your program may need
read and write access to the same data file.
Rules at a Glance
Use the
Lock
procedure with only thefilenumber
argument to lock the whole file.record
is interpreted as a record number in the case of random files and a byte number in the case of binary files. Records and bytes in a file are always numbered sequentially from 1 onward.To lock a particular record, specify its record number as
record
, and only that record will be locked.The
Lock
procedure locks an entire file opened in Input or Output (sequential) mode, regardless of therecord
argument.If you omit the
start
argument,Lock
will lock all records from the start of the file to record or byte numberend
.Attempting to access a locked file or portion of a file returns runtime error 70, “Permission denied.”
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