@LINES

@LINES[filename]:  Returns the line number of the last line in the file, 
or "-1" if the file is empty.  The first line in the file is numbered 0, 
so (for example) @LINES will return 0 for a file containing one line.  To 
get the actual number of lines, use %@INC[%@LINES[filename]]. 

@LINES works with files having lines of no more than 1023 characters; 
longer lines will not be counted accurately. 

@LINES must read each line of the file in order to count it, and will 
therefore cause significant delays if used in a long loop or on a large 
file.