这个脚本中f.seek(0)的目的是什么？为什么我们需要倒带(current_file),如果该文件已被程序打开？
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)