file_length - get the number of lines in a file

int file_length( string file );

file_length() returns the number of lines in file 'file'.  Size -1
indicates that 'file' either does not exist, or that it is not
readable. Size -2 indicates that 'file' is a directory.

Note that this efun is not particularly fast on long files, since
determining the number of lines requires reading the entire file.

See also:
 file_size,
 stat,
 get_dir
