READBLK

Top  Previous  Next

 

The READBLK statement reads a given number of bytes from the current file position in a record previously opened using OPENSEQ.

 

 

Format

 

READBLK var FROM file.var, bytes

{ON ERROR statement(s)}

{THEN statement(s)}

{ELSE statement(s)}

 

where

 

varis the name of a variable to receive the data read from the file.

 

file.varis the file variable associated with the file.

 

bytesevaluates to the number of bytes to be read.

 

statement(s)are statements to be executed depending on the outcome of the READBLK operation.

 

At least one of the THEN and ELSE clauses must be present.

 

The THEN clause is executed if the READBLK is successful.

 

The ELSE clause is executed if the READBLK fails. The  STATUS()function will indicate the cause of the error.

 

The ON ERROR clause is executed for serious fault conditions such as errors in a file's internal control structures. The STATUS() function will return an error number. If no ON ERROR clause is present, an abort would occur.

 

 

If file.var refers to a serial port opened using OPENSEQ, the READBLK statement reads up to bytes bytes of data from the port but does not wait if there is less than the requested number of bytes available.

 

 

Example

 

READBLK VAR FROM SEQ.F, 100 THEN

  ...processing statements...

END ELSE

  DISPLAY "Data block not read"

END

 

This program fragment reads 100 bytes from the a file previously opened to file variable SEQ.F into variable VAR.

 

 

See also:

CLOSESEQ, NOBUF, OPENSEQ, READCSV, READSEQ, SEEK, WEOFSEQ, WRITEBLK, WRITECSV, WRITESEQ, WRITESEQF