LOCK (access)

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A LOCK access READ or WRITE can be specified in a file OPEN statement in a network environment(DOS 3.1 or higher).

Valid Options:

  • Default: When LOCK is not specified in an OPEN statement, all other processes are denied file access.
  • SHARED: When specified, any file can be READ or WRITE accessed by other procedures.
  • LOCK READ: When specified, read access is denied to other file procedures.
  • LOCK WRITE: When specified, write access is denied to other file procedures.
  • LOCK READ WRITE: When specified any access is denied to other file procedures.


  • Requires that the DOS SHARED.EXE program be run for QBasic to use networking access modes.
  • If another process already has access to a specified file, program access is denied for that file OPEN statement. A "Permission Denied" error 70 will be returned. A network program must be able to handle a denial of access error.

See also: LOCK (statement), ACCESS (clause), ON ERROR


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