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Seek statement

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Sets the position for the next read/write operation within a file opened by using the Open statement.

Syntax

Seek [ # ] filenumber, position

The Seek statement syntax has these parts:

Part Description
filenumber Required. Any valid file number.
position Required. Number in the range 1 – 2,147,483,647, inclusive, that indicates where the next read/write operation should occur.

Remarks

Record numbers specified in Get and Put statements override file positioning performed by Seek.

Performing a file-write operation after a Seek operation beyond the end of a file extends the file. If you attempt a Seek operation to a negative or zero position, an error occurs.

Example

This example uses the Seek statement to set the position for the next read or write within a file. This example assumes that TESTFILE is a file containing records of the user-defined type Record.

Type Record ' Define user-defined type. 
 ID As Integer 
 Name As String * 20 
End Type

For files opened in Random mode, Seek sets the next record.

Dim MyRecord As Record, MaxSize, RecordNumber ' Declare variables. 
' Open file in random-file mode. 
Open "TESTFILE" For Random As #1 Len = Len(MyRecord) 
MaxSize = LOF(1) \ Len(MyRecord) ' Get number of records in file. 
' The loop reads all records starting from the last. 
For RecordNumber = MaxSize To 1 Step - 1 
 Seek #1, RecordNumber ' Set position. 
 Get #1, , MyRecord ' Read record. 
Next RecordNumber 
Close #1 ' Close file.

For files opened in modes other than Random mode, Seek sets the byte position at which the next operation takes place. This example assumes that TESTFILE is a file containing a few lines of text.

Dim MaxSize, NextChar, MyChar 
Open "TESTFILE" For Input As #1 ' Open file for input. 
MaxSize = LOF(1) ' Get size of file in bytes. 
' The loop reads all characters starting from the last. 
For NextChar = MaxSize To 1 Step -1 
 Seek #1, NextChar ' Set position. 
 MyChar = Input(1, #1) ' Read character. 
Next NextChar 
Close #1 ' Close file.

See also

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