AT&T 6300 Programmer's Manual page 345

Syntax
Remarks
Example
LOF
Function
Returns the length of the named file in bytes.
LOF(filenum)
For disk files LOF returns the actual numbers
of bytes allocated to the file.
For communications files LOF returns the
amount of file space in the input buffer. The
actual value returned is:
buffersize-LOC(filenum)
Where "buffersize" is the size of the
communications buffer. It defaults to 256
bytes, but may be changed with the "/C:"
option in the GWBASIC command line.
10 OPEN uB:MYFILE" AS #2
20 GET #2,LOF[2]/128
The above statements will get the last record
of the file MYFILE (residing on the diskette
inserted in drive B) assuming that the file was
created with a record length of 128 bytes.
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