>The fastest method is to count the number of characters. If you count the number of lines you always have to read the file twice.
>
>nRead=0
>nFileLength=fseek(nFileHandle, 0, 2)
>=fseek(nFileHandle, 0, 0) && go top
>
>** DO WHILE NOT EOF
> nRead=nRead+MyReadLine(nFileHandle, ...) && returns lenghts of line
> SetThermometer(100 * nRead / nFileLength)

Yes, this is what I have implemented. The thermometer is not regular but works fine until 100%.