VB.NET Language in a Nutshell, Second Edition

Name

Seek Procedure

Class

Microsoft.VisualBasic.FileSystem

Syntax

Seek(filenumber, position)

filenumber (required; Integer)

Any valid file number

position (required; Long)

Any whole number between 1 and 2,147,483,647

Description

Places the read/write marker at a given position where the next read/write operation should occur

Rules at a Glance

• If the file has been opened in Random mode, position refers to the next record number that should be read or written.

• In all other file open modes (Append, Binary, Input, and Output), position is the byte where the next read or write operation will start.

• The use of a record number in any subsequent FileGet or FilePut procedure overrides the position set by the Seek procedure.

• The size of a file can be increased as the result of a write operation that is performed after a call to the Seek procedure in which position is beyond the end of the file.

• If position is 0 or negative, a runtime error will be generated.

Programming Tips and Gotchas

Unused records in a random-access data file are not necessarily blank. For example, if you open a brand new data file, then perform a seek operation to record number 10 and write a new record, the preceding 9 records will be filled with binary data that was present on the section of the disk used by the new file prior to its creation.

See Also

Seek Function