在 Ruby 中编辑文件中的每一行

问题描述

我试图找到一种简单的方法来编辑文件中的每一行，但我在理解如何使用 File 类来执行此操作时遇到了一些麻烦.

I'm trying to find a simple way of editing each line in a file, and I'm having some trouble understanding how to use the File class to do so.

我要编辑的文件有几百行，每行都有逗号分隔值.我只对每一行中的第一个值感兴趣，我想删除第一个值之后的所有值.我尝试执行以下操作:

The file I want to edit has several hundred lines with comma separated values in each line. I'm only interested in the first value in each line, and I want to delete all values after the first one. I tried to do the following:

File.open('filename.txt', 'r+') do |file|
  file.each_line { |line| line = line.split(",")[0] }
  file.write
  file.close
end

这不起作用，因为 File.write 方法需要将内容作为参数写入.

Which doesn't work because File.write method requires the contents to be written as an argument.

有人能告诉我如何才能达到预期的效果吗?

Could someone enlighten me as to how I could achieve the desired effect?

推荐答案

更好(也是最安全)的解决方案之一是使用 TempFile，并将其移动到原始位置(使用 FileUtils) 完成后:

The one of the better solutions(and safest) is to create a temporary file using TempFile, and move it to the original location(using FileUtils) once you are done:

   require 'fileutils'
   require 'tempfile'

    t_file = Tempfile.new('filename_temp.txt')
    File.open("filename.txt", 'r') do |f|
      f.each_line{|line| t_file.puts line.split(",")[0].to_s }
    end
    t_file.close
    FileUtils.mv(t_file.path, "filename.txt")

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