QBasic 1.1: LOCK Statement

Explanation

LOCK, UNLOCK Statements

LOCK limits or prevents access to a file by a network process. UNLOCK releases the locks imposed by the last LOCK statement.

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Syntax

LOCK [#]filenumber% [,{record& | [start&] TO end&}]

UNLOCK [#]filenumber% [,{record& | [start&] TO end&}]

Description / Parameter(s)

filenumber%	The number of an open file.
record&	For random-access files, the number of a record to lock, relative to the first record in the file. For binary files, the number of a byte to lock, relative to the first byte in the file.
start& and end&	The numbers of the first and last records or bytes in a range of records or bytes to lock or unlock.
For sequential files, LOCK and UNLOCK affect the entire file.

Example


'This example runs only in a network environment.
OPEN "TEST.DAT" FOR RANDOM AS #1
FOR i% = 1 TO 10
  PUT #1, , i%
NEXT i%
LOCK #1, 2         'Lock record 2.
GET #1, 2, i%
UNLOCK #1, 2       'Unlock record 2.