Location of the position indicator in a file.
POSITION = FTELL(FID) returns the location of the file position
indicator in the specified file. Position is indicated in bytes
from the beginning of the file. If -1 is returned, it indicates
that the query was unsuccessful; use FERROR to determine the nature
of the error.
FID is an integer file identifier obtained from FOPEN , or 0 for
standard input, 1 for standard output or 2 for standard error.
See also FOPENZTI1WQ, FSEEK .