shell每n行插入一行 [英] shell insert a line every n lines

问题描述

我有两个文件，我试图从file2插入一行到file1，每隔4行从file1开始。例如：

file1：

 第1行
线2 
线3 
线4 
线5 
线6 
线7 
线8 
线9 
线10 
  

file2：

  50 
 43 
 21 
  

得到：

  50 
线1 
线2 
线3 
第4行
 43 
行5 
行6 
行7 
行8 
 21 
行9 
行10 
  

我有这个代码：

  while read line 
 do 
 sed'0〜4 s / $ / $ line / g'< file1.txt> file2.txt 
完成< file1.txt 
  

我得到以下错误：

  sed：1：0〜4 s / $ / $ line / g：无效的命令代码〜
   $ b 
解决方案
下面的步骤通过这两个文件，不加载任何一个到内存中的数组：
 
 
  awk'（NR-1）％4 == 0 {getline this   
如果您的实际 file2 大于您想要保存的内存。
 
 
这个分解如下： 
 
 
 
 
  （NR-1）％4 == 0   - 匹配从第4行开始的每一行的条件 
 
  getline this<file2   - 从file2中获取一行并将其存储在变量 this 中
 
 
 打印这个  - 打印...这个。
 
 
  1 当前行，在这种情况下来自file1（awk正常的输入）
 
 
 
I have two files and I am trying to insert a line from file2 into file1 every other 4 lines starting at the beginning of file1. So for example:

file1:
line 1
line 2
line 3
line 4
line 5
line 6
line 7
line 8
line 9
line 10
file2:
50
43
21
output I am trying to get:
50
line 1
line 2
line 3
line 4
43
line 5
line 6
line 7
line 8
21
line 9
line 10
The code I have:
while read line
do
    sed '0~4 s/$/$line/g' < file1.txt > file2.txt
done < file1.txt
I am getting the following error:
sed: 1: "0~4 s/$/$line/g": invalid command code ~

解决方案
The following steps through both files without loading either one into an array in memory:
awk '(NR-1)%4==0{getline this<"file2";print this} 1' file1
This might be preferable if your actual file2 is larger than what you want to hold in memory.

This breaks down as follows:


(NR-1)%4==0 - a condition which matches every 4th line starting at 0
getline this<"file2" - gets a line from "file2" and stores it in the variable this
print this - prints ... this.
1 - shorthand for "print the current line", which in this case comes from file1 (awk's normal input)


                        
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