习题 20 函数和文件
# ex20.rb
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 puts three lines:"
current_line = 1
print_a_line(current_line, current_file)
current_line = current_line + 1
print_a_line(current_line, current_file)
current_line = current_line + 1
print_a_line(current_line, current_file)
test.txt
This is line 1
This is line 2
This is line 3
结果：
$ 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 puts three lines:
1, This is line 1
2, This is line 2
3, This is line 3
