SEEK Statement
 ----------------------------------------------------------------------------


 Action

 Sets the position in a file for the next read or write.


 Syntax



  SEEK #  filenumber%,  position&

 Remarks


 The  SEEK statement uses the following arguments.

-----------------------------------------------------------------------------
 Argument                                Description
 ----------------------------------------------------------------------------
 Argument                                Description
 ----------------------------------------------------------------------------
  filenumber%                            The number used in the  OPEN
                                         statement to open the file.

  position&                              A numeric expression that
                                         indicates where the next read or
                                         write occurs. The  position& value
                                         must be between 1 and
                                         2,147,483,647 (equivalent to 231
                                         -1), inclusive.





 For files opened in random-access mode,  position& is the number of a record
 in the file.

 For files opened in binary, input, output, or append mode,  position& is the
 byte position relative to the beginning of the file. The first byte in a
 file is at position 1; the second byte is at position 2, and so on. After a
 SEEK operation, the next file I-O operation starts at the specified byte
 position.


 Note

 Record numbers on a  GET or  PUT override the file positioning done by
 SEEK.

 Performing a file write after doing a  SEEK operation beyond the end of a
 file extends the file. If you attempt a  SEEK operation to a negative or
 zero position, BASIC generates the error message Bad record number.

 BASIC leaves the file position unchanged when you use  SEEK on an ISAM table
 or on BASIC devices (SCRN, CONS, KYBD, COM n, LPT n, PIPE) that do not
 support  SEEK.


 See Also

  GET (File I-O);  OPEN;  PUT (File I-O);  SEEK Function;  SEEKGT,  SEEKGE,
 SEEKEQ Statements



 Example

 The following example uses a combination of the  SEEK function and  SEEK
 statement to move the file position exactly one record back and rewrite the
 record if a variable is true (nonzero).

 CONST FALSE = 0, TRUE = NOT FALSE


 ' Define record fields and a user-type variable.


 TYPE TestRecord


    NameField  AS STRING * 20


    ScoreField AS SINGLE


 END TYPE


 DIM RecordVar AS TestRecord


 DIM I AS LONG


 ' This part of the program creates the random-access file used by the


 ' second part of the program, which demonstrates the SEEK statement.


 OPEN "TESTDAT2.DAT" FOR RANDOM AS #1 LEN = LEN(RecordVar)


 RESTORE


 READ NameField$, ScoreField


 I = 0


 DO WHILE NameField$ <> "END"


    I = I + 1


    RecordVar.NameField = NameField$


    RecordVar.ScoreField = ScoreField


    PUT #1, I, RecordVar


    READ NameField$, ScoreField


 LOOP


 CLOSE #1


   DATA "John Simmons", 100


   DATA "Allie Simpson", 95


   DATA "Tom Tucker", 72


   DATA "Walt Wagner", 90


   DATA "Mel Zucker", 92


   DATA "END", 0





 ' Open the test data file.


 DIM FileBuffer AS TestRecord


 OPEN "TESTDAT2.DAT" FOR RANDOM AS #1 LEN = LEN(FileBuffer)


 ' Calculate number of records in the file.


 Max = LOF(1) \ LEN(FileBuffer)


 ' Read and print contents of each record.


 FOR I = 1 TO Max


    GET #1, I, FileBuffer


    IF FileBuffer.NameField = "Tom Tucker" THEN


       ReWriteFlag = TRUE


       EXIT FOR


    END IF


 NEXT I


 IF ReWriteFlag = TRUE THEN


    ' Back up file by the length of the record variable that


    ' is used to write to the file.


    FileBuffer.ScoreField = 100


    SEEK #1, SEEK(1) - LEN(RecordVar)


    PUT #1, , RecordVar


 END IF


 CLOSE #1


 KILL "TESTDAT2.DAT"


 END