LOCK

The LOCK statement restricts access to parts of a file by other programs or processes.

Syntax

LOCK [#]fileNumber%

LOCK [#]fileNumber%, record&

LOCK [#]fileNumber%, [firstRecord&] TO lastRecord&

Description

• fileNumber% is the file number of the file to lock.
• In the first syntax, the entire file is locked.
• In the second syntax, record& is the record number of the file to lock.
• In the third syntax, the records or bytes in the range [firstRecord&,lastRecord&] are locked. If firstRecord& is omitted, it is assumed to be one (the first record or byte).
• For files opened in BINARY mode, each record corresponds to a single byte.
• LOCK and UNLOCK statements are always used in pairs and each statement must match the other one.
• Files must be unlocked using UNLOCK before other programs can access them, and before the file is closed.
• Keyword not supported in Linux or macOS versions

QBasic/QuickBasic

• Required DOS SHARED.EXE to be run for QBasic to use networking access modes. No longer required.

See also

• UNLOCK
• OPEN
• ACCESS

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