what is the purpose of f.seek(0) in this script? Why do we need to rewind(current_file), if the file has already been opened by the program?
input_file = ARGV[0]
def print_all(f)
puts f.read()
end
def rewind(f)
f.seek(0)
end
def print_a_line(line_count,f)
puts "#{line_count} #{f.readline()}"
end
current_file = File.open(input_file)
puts "First Let's print the whole file:"
puts # a blank line
print_all(current_file)
puts "Now Let's rewind, kind of like a tape"
rewind(current_file)
puts "Let's print the first line:"
current_line = 1
print_a_line(current_line, current_file)
It seeks ("goes to", "attempts to find") a given position (as integer) in a stream. In your code you define a new method called rewind which takes one argument. When you call it with
rewind(current_file)
you send the current_file (the one you have opened from disk or from anywhere else) which is defined as:
current_file = File.open(input_file)
to the rewind method and it will "seek" to position 0 which is the beginning of the file.
You could also create another method called almost_rewind and write:
def almost_rewind(f)
f.seek(-10, IO::SEEK_END)
end
This would go 10 positions backwards in your stream, starting from the END of the stream.