The CountLines(file) command counts the number of lines from the current position in file to the end of file.

A line is defined to be zero or more characters delimited by the current file position, a new line character, and the end of file.  There is one exception to this definition: if the last character in the file is a newline, then the null string (zero characters) between this newline and the end of file is not considered a line. This definition is consistent with the behavior of ReadLine and readline.

An error is raised if file is not a valid descriptor or if it is the name of a file that does not exist.