#输出222.rb的内容
File.open("222.rb","r+") do |file|
while line = file.gets
puts line
end
end

#直接用IO操作文件
IO.foreach("222.rb") do |line|
puts line if line =~/abc/ #输出匹配到了'abc'的所在行
puts line if line !~/qwe/ #输出没有匹配到'qwe'的所在行
end

#输出文件的绝对路径
puts File.expand_path("222.rb")

#count chars from a file
file= File.new("222.rb")
w_count = 0
file.each_byte do |byte|
w_count += 1 if byte ==?1
end
puts "#{w_count}"

#create new file and write some words there
print "The file now is exist? --> " 
puts File.exist?("asd.txt")#判断文件是否存在

file= File.new("asd.txt","w")
print "The file now is exist? --> " 
puts File.exist?("asd.txt")

file.write("hehe\nhahah")

#io.stream operation
require 'stringio'
ios = StringIO.new("abcdef\n ABC \n 12345")
ios.seek(5) #把偏移指针移到5（e字母所在位置）
ios.puts("xyz3") #从5开始覆写原有数据
puts ios.tell #tell--Returns the current offset (in bytes) of ios. 
puts ios.string
puts ios.string.dump #忽略\n的转义

#another example
require 'stringio'
ios = StringIO.new("abcdef\nq9ert \n 12345")
ios.seek(3)
ios.ungetc(?w) #replace the char at index 3
puts "Ptr = #{ios.tell}"
s1 = ios.gets #filte the "\n" 
s2 = ios.gets
puts s1
puts s2

#Ruby打开文件并写入数据操作
txt = File.open("文件路径","w+")
txt.puts '要写入的文件内容'
txt.close
#从文件里读取数据
num = File.readlines("文件路径")[0].chomp
#打开文件的方法
system("notepad 文件路径")