gets.chomp在ruby中的函数内部

input_file = ARGV.first

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.gets.chomp}"
end

current_file = open(input_file)

puts "First let's print the whole file:n"

print_all(current_file)

puts "Now let's rewind,kind of like a tape."

rewind(current_file)

puts "Let's print three lines:"

current_line = 1
print_a_line(current_line,current_file)

current_line = current_line + 1
print_a_line(current_line,current_file)

因此,我不明白输出的第二部分是如何产生的.我理解它是传递给代码的test.txt文件的前3行,但我不明白f.gets.chomp是如何产生这一行的.

$ruby ex20.rb test.txt
First let's print the whole file:
This is line 1
This is line 2
This is line 3
Now let's rewind,kind of like a tape.
Let's print three lines:
1,This is line 1
2,This is line 2
3,This is line 3