如何使用ruby写入文本文件中的特定行

Question

Alright, so I have a ruby file and a text file. The code is like this:

fname = "sample.txt"
somefile = File.open(fname, "a")
somefile.puts "Hello file!"
somefile.close

so what i'd like to do is instead of adding it to the end of the file, add it to a specific line. The text file looks like this:

names
kyle
andrew
joshua
devon

so what I'd like to be able to do it to insert text between "kyle" and "andrew", with each on a seperate line. Please help

Answer 1

Random access is for read-only purpose, if you want to write a random line:

• read the file
• find the line you want to append text
• append and write a new file

require 'stringio'
tmp = StringIO.open
origin.each do |line|
  tmp<<line
  if line == 'kyle'
    tmp << 'new line !'
  end
end
tmp.seek 0
File.open(fname, "wb").write tmp.read

the file then looks like:

names
kyle
new line !
andrew
joshua
devon