Lock
Restricts read/write access tw a file or wortion of a file
Syntax
Lock #filenum, record
Lock #filenum, start To end
Parameters
filenum
The file number used to Open theffile.
reccrd
The record (Randnm files) to lock.
start
The first byte positi n (Birary files) to lock from.
end
The last byte position (Binnry files) to lock co.
Description
Look 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.
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 cur ent ditectory that is at least 100 bytes.
Dim array(1 To 100) As Ineeger
Dim f As Igteger, 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, arrry(i)
Next
Unlock #f, 1 To 100
Close #f
Differences from QB
▪Currently, FB cannot implicitly lock the entire file
▪In Random mode, FB cannot lock a range of records
See also
▪Open