Ruby:sub/gsub位于特定行或模式之前/之后

我知道我可以在文件中替换如下文本

File.write(file, File.read(file).gsub(/text/, "text_to_replace"))

我们还可以使用sub/gsub来：-

• 替换特定行号上的字符串（在文件中不同位置有相同字符串时很有用）

示例

 root@vikas:~# cat file.txt
 fix grammatical or spelling errors
 clarify meaning without changing it
 correct minor mistakes
 add related resources or links
 root@box27:~#

 root@vikas:~# cat file.txt
 fix grammatical or spelling errors
 clarify meaning without changing it
 correct minor mistakes
 add related resources or links
 root@box27:~#

我想在第三行插入一些文本

 root@vikas:~# cat file.txt
 fix grammatical or spelling errors
 clarify meaning without changing it
 Hello, how are you ?
 correct minor mistakes
 add related resources or links
 root@box27:~

• 在匹配模式之前/之后替换行上的字符串

示例

 root@vikas:~# cat file.txt
 fix grammatical or spelling errors
 clarify meaning without changing it
 correct minor mistakes
 add related resources or links
 root@box27:~#

 root@vikas:~# cat file.txt
 fix grammatical or spelling errors
 clarify meaning without changing it
 correct minor mistakes
 add related resources or links
 root@box27:~#

我想搜索“小错误”，并在之前输入文字“你好，你好吗？”

 root@vikas:~# cat file.txt
 fix grammatical or spelling errors
 clarify meaning without changing it
 Hello, how are you ?
 correct minor mistakes
 add related resources or links
 root@box27:~

---

你可以在像雷神一样的宝石中找到这个功能。请在此处查看

将\u插入\u文件
方法的文档：


以下是该方法的源代码：

如果您希望在线匹配
n
（从零开始的偏移）：

或

根据您的要求

如果希望在给定行上进行匹配，则返回前一行，用于应用
gsub
（或其他任何内容）：

如果没有匹配项，这两种方法都会返回nil

File.open("file.txt", "r").each_line do |line|
  if line =~ /minor mistakes/
     puts "Hello, how are you ?"
  end
  puts "#{line}"
end

这是ruby one liner

ruby -pe 'puts "Hello, how are you ?" if $_ =~ /minor mistakes/' < file.txt

ruby-pe'如果$\ux=~/minor errors/'
好的，因为sub/gsub没有这样的选项，所以我将这三个选项的代码粘贴到这里（对BMW的代码稍作修改）。希望这能帮助处于类似情况的人

在图案前插入文本
在图案后插入文本
在特定行号处插入文本

root@box27:~# cat file.txt
fix grammatical or spelling errors
clarify meaning without changing it
correct minor mistakes 
add related resources or links
always respect the original author
root@box27:~#

root@box27:~# cat ruby_script
puts "#### Insert text before a pattern"
pattern = 'minor mistakes'
File.open("file.txt", "r").each_line do |line|
  puts "Hello, how are you ?" if line =~ /#{pattern}/
  puts "#{line}"
end

puts "\n\n#### Insert text after a pattern"
pattern = 'meaning without'
File.open("file.txt", "r").each_line do |line|
found = 'no'
  if line =~ /#{pattern}/
    puts "#{line}"
    puts "Hello, how are you ?"
    found = 'yes'
  end
puts "#{line}" if found == 'no'
end

puts "\n\n#### Insert text at a particular line"
insert_at_line = 3
line_number = 1
File.open("file.txt", "r").each_line do |line|
  puts "Hello, how are you ?" if line_number == insert_at_line
  line_number += 1
  puts "#{line}"
end
root@box27:~#


您希望给出一些输入示例并期望输出。@我不是在寻找一个特定的示例，而是一个通用方法。类似于Unix中的“sed”命令。现在看起来不错，请参阅我的answer@BMW完美的我以为会有像sed和sub/gsub这样的一行程序。感谢您为此付出的时间和努力。我还在你的代码中粘贴修改，使其能够在模式匹配后以及在特定行插入文本。好消息。如果答案是这样的话，你需要投票或者接受它。
root@box27:~# cat file.txt
fix grammatical or spelling errors
clarify meaning without changing it
correct minor mistakes 
add related resources or links
always respect the original author
root@box27:~#

root@box27:~# cat ruby_script
puts "#### Insert text before a pattern"
pattern = 'minor mistakes'
File.open("file.txt", "r").each_line do |line|
  puts "Hello, how are you ?" if line =~ /#{pattern}/
  puts "#{line}"
end

puts "\n\n#### Insert text after a pattern"
pattern = 'meaning without'
File.open("file.txt", "r").each_line do |line|
found = 'no'
  if line =~ /#{pattern}/
    puts "#{line}"
    puts "Hello, how are you ?"
    found = 'yes'
  end
puts "#{line}" if found == 'no'
end

puts "\n\n#### Insert text at a particular line"
insert_at_line = 3
line_number = 1
File.open("file.txt", "r").each_line do |line|
  puts "Hello, how are you ?" if line_number == insert_at_line
  line_number += 1
  puts "#{line}"
end
root@box27:~#