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Visual Basic for Applications Reference

Visual Studio 6.0

Lock, Unlock Statements

See Also    Example    Specifics

Controls access by other processes to all or part of a file opened using the Open statement.

Syntax

Lock [#]filenumber[, recordrange]
. . .

Unlock [#]filenumber[, recordrange]

The Lock and Unlock statement syntax has these parts:

Part Description
filenumber Required. Any valid file number.
recordrange Optional. The range of records to lock or unlock.

Settings

The recordrange argument settings are:

recnumber | [start] To end

Setting Description
recnumber Record number (Random mode files) or byte number (Binary mode files) at which locking or unlocking begins.
start Number of the first record or byte to lock or unlock.
end Number of the last record or byte to lock or unlock.

Remarks

The Lock and Unlock statements are used in environments where several processes might need access to the same file.

Lock and Unlock statements are always used in pairs. The arguments to Lock and Unlock must match exactly.

The first record or byte in a file is at position 1, the second record or byte is at position 2, and so on. If you specify just one record, then only that record is locked or unlocked. If you specify a range of records and omit a starting record (start), all records from the first record to the end of the range (end) are locked or unlocked. Using Lock without recnumber locks the entire file; using Unlock without recnumber unlocks the entire file.

If the file has been opened for sequential input or output, Lock and Unlock affect the entire file, regardless of the range specified by start and end.

Caution   Be sure to remove all locks with an Unlock statement before closing a file or quitting your program. Failure to remove locks produces unpredictable results.

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