head function
Prepares to read count lines from the file at path.
The head function returns a HeadProgress which can
then be used to read the configured lines via one of HeadProgress
methods.
head('/var/log/syslog', 10).forEach((line) => print(line));
Throws a core.HeadException exception if path is not a file.
Implementation
HeadProgress head(String path, int lines) =>
HeadProgress._internal(path, lines);