filename = ARGV.first
txt = open(filename)
puts "Here's your file #{filename}:"
print txt.read
print "Type the filename again: "
file_again = $stdin.gets.chomp
txt_again = open(file_again)
print txt_again.read
命令行执行： ruby ex15.rb ex15_sample.txt
从命令行参数获得要读取的文件名，避免hard code（程序员最讨厌的事情之一）
一段实现简单的文件编辑器代码
filename = ARGV.first
puts "We're going to erase #{filename}"
puts "If you don't want that, hit CTRL-C (^C)."
puts "If you do want that, hit RETURN."
$stdin.gets
puts "Opening the file..."
target = open(filename, 'w')
puts "Truncating the file. Goodbye!"
target.truncate(0)
puts "Now I'm going to ask you for three lines."
print "line 1: "
line1 = $stdin.gets.chomp
print "line 2: "
line2 = $stdin.gets.chomp
print "line 3: "
line3 = $stdin.gets.chomp
puts "I'm going to write these to the file."
target.write(line1)
target.write("\n")
target.write(line2)
target.write("\n")
target.write(line3)
target.write("\n")
puts "And finally, we close it."
target.close
一段实现拷贝文件的代码
from_file, to_file = ARGV
puts "Copying from #{from_file} to #{to_file}"
# we could do these two on one line, how?
in_file = open(from_file)
indata = in_file.read
puts "The input file is #{indata.length} bytes long"
puts "Does the output file exist? #{File.exist?(to_file)}"
puts "Ready, hit RETURN to continue, CTRL-C to abort."
$stdin.gets
out_file = open(to_file, 'w')
out_file.write(indata)
puts "Alright, all done."
out_file.close
in_file.close
echo "This is a test file." > test.txt
cat test.txt
ruby ex17.rb test.txt new_file.txt
# this one is like your scripts with ARGV
def print_two(*args)
arg1, arg2 = args
puts "arg1: #{arg1}, arg2: #{arg2}"
end
# ok, that *args is actually pointless, we can just do this
def print_two_again(arg1, arg2)
puts "arg1: #{arg1}, arg2: #{arg2}"
end
# this just takes one argument
def print_one(arg1)
puts "arg1: #{arg1}"
end
# this one takes no arguments
def print_none()
puts "I got nothin'."
end
print_two("Zed","Shaw")
print_two_again("Zed","Shaw")
print_one("First!")
print_none()
def cheese_and_crackers(cheese_count, boxes_of_crackers)
puts "You have #{cheese_count} cheeses!"
puts "You have #{boxes_of_crackers} boxes of crackers!"
puts "Man that's enough for a party!"
puts "Get a blanket.\n"
end
puts "We can just give the function numbers directly:"
cheese_and_crackers(20, 30)
puts "OR, we can use variables from our script:"
amount_of_cheese = 10
amount_of_crackers = 50
cheese_and_crackers(amount_of_cheese, amount_of_crackers)
puts "We can even do math inside too:"
cheese_and_crackers(10 + 20, 5 + 6)
puts "And we can combine the two, variables and math:"
cheese_and_crackers(amount_of_cheese + 100, amount_of_crackers + 1000)
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)
current_line = current_line + 1
print_a_line(current_line, current_file)
前面我们讲过用 ＝ 设定变量的用法，变量也支持函数的返回值（return）
def add(a, b)
puts "ADDING #{a} + #{b}"
return a + b
end
def subtract(a, b)
puts "SUBTRACTING #{a} - #{b}"
return a - b
end
def multiply(a, b)
puts "MULTIPLYING #{a} * #{b}"
return a * b
end
def divide(a, b)
puts "DIVIDING #{a} / #{b}"
return a / b
end
puts "Let's do some math with just functions!"
age = add(30, 5)
height = subtract(78, 4)
weight = multiply(90, 2)
iq = divide(100, 2)
puts "Age: #{age}, Height: #{height}, Weight: #{weight}, IQ: #{iq}"
# A puzzle for the extra credit, type it in anyway.
puts "Here is a puzzle."
what = add(age, subtract(height, multiply(weight, divide(iq, 2))))
puts "That becomes: #{what}. Can you do it by hand?"
读懂每一行代码
puts "Let's practice everything."
puts 'You\'d need to know \'bout escapes with \\ that do \n newlines and \t tabs.'
poem = <<END
\tThe lovely world
with logic so firmly planted
cannot discern \n the needs of love
nor comprehend passion from intuition
and requires an explanation
\n\t\twhere there is none.
END
puts "--------------"
puts poem
puts "--------------"
five = 10 - 2 + 3 - 6
puts "This should be five: #{five}"
def secret_formula(started)
jelly_beans = started * 500
jars = jelly_beans / 1000
crates = jars / 100
return jelly_beans, jars, crates
end
start_point = 10000
beans, jars, crates = secret_formula(start_point)
puts "With a starting point of: #{start_point}"
puts "We'd have #{beans} beans, #{jars} jars, and #{crates} crates."
start_point = start_point / 10
module Ex25
# This function will break up words for us.
def Ex25.break_words(stuff)
words = stuff.split(' ')
return words
end
# Sorts the words.
def Ex25.sort_words(words)
return words.sort
end
# Prints the first word after shifting it off.
def Ex25.print_first_word(words)
word = words.shift
puts word
end
# Prints the last word after popping it off.
def Ex25.print_last_word(words)
word = words.pop
puts word
end
# Takes in a full sentence and returns the sorted words.
def Ex25.sort_sentence(sentence)
words = Ex25.break_words(sentence)
return Ex25.sort_words(words)
end
# Prints the first and last words of the sentence.
def Ex25.print_first_and_last(sentence)
words = Ex25.break_words(sentence)
Ex25.print_first_word(words)
Ex25.print_last_word(words)
end
# Sorts the words then prints the first and last one.
def Ex25.print_first_and_last_sorted(sentence)
words = Ex25.sort_sentence(sentence)
Ex25.print_first_word(words)
Ex25.print_last_word(words)
end
end
irb
require "./ex25.rb"