如何使用AWK从文件连续输出行 [英] How to use AWK to continuously output lines from a file

问题描述

我有一个包含多行的文件，并且我想连续输出文件的某些行，例如第一次，从第一行打印到第五行，下一次，第二行打印到第六行，依此类推.我发现AWK是一个非常有用的功能，我尝试自己编写代码，但是它什么也没输出.以下是我的代码

I have a file with multiple lines, and I want to continuously output some lines of the file, such as first time, print from line 1 to line 5, next time, print line 2 to line 6, and so on. I find AWK as a very useful function and I tried to write a code on my own, but it just outputs nothing. Following is my code

#!/bin/bash
for n in `seq 1 3`
do
  N1=$n
  N2=$((n+4))
  awk -v n1="$N1" -v n2="$N2" 'NR == n1, NR == n2 {print $0}' my_file >> new_file
done

例如，我有一个名为my_file的输入文件

For example, I have an input file called my_file

1 99 tut
2 24 bcc
3 32 los
4 33 rts
5 642 pac
6 23 caas
7 231 cdos
8 1 caee
9 78 cdsa

然后我希望输出文件为

1 99 tut
2 24 bcc
3 32 los
4 33 rts
5 642 pac
2 24 bcc
3 32 los
4 33 rts
5 642 pac
6 23 caas
3 32 los
4 33 rts
5 642 pac
6 23 caas
7 231 cdos

推荐答案

能否请您按照GNU awk 中显示的示例进行尝试，编写和测试.在需要提及所有需要在 lines_from 变量中打印的行的地方，有一个名为 till_lines 的变量，它告诉我们从一个特定的行需要打印多少行行(例如，从第一行开始的>也将打印下4行).另一方面，我已经测试了OP的代码，它对我来说很好用，因为它使用new_file生成输出文件，因为在bash循环中调用 awk 并不是一个好习惯，因此在这里也进行了改进./p>

Could you please try following, written and tested with shown samples in GNU awk. Where one needs to mention all lines which needs to be printed in lines_from variable, then there is a variable named till_lines which tells us how many lines we need to print from a specific line(eg--> from 1st line print next 4 lines too). On another note, I have tested OP's code and it worked fine for me, its generating the output file with new_file since calling awk in bash loop is NOT good practice hence adding this as an improvement too here.

awk -v lines_from="1,2,3" -v till_lines="4" '
BEGIN{
  num=split(lines_from,arr,",")
  for(i=1;i<=num;i++){ line[arr[i]] }
}
FNR==NR{
  value[FNR]=$0
  next
}
(FNR in line){
  print value[FNR] > "output_file"
  j=""
  while(++j<=till_lines){ print value[FNR+j] > "output_file" }
}
'  Input_file  Input_file

当我看到 output_file 的内容时，我会看到以下内容:

When I see contents of output_file I could see following:

cat output_file
1 99 tut
2 24 bcc
3 32 los
4 33 rts
5 642 pac
2 24 bcc
3 32 los
4 33 rts
5 642 pac
6 23 caas
3 32 los
4 33 rts
5 642 pac
6 23 caas
7 231 cdos

说明: 添加以上详细说明.

Explanation: Adding detailed explanation for above.

awk -v lines_from="1,2,3" -v till_lines="4" '    ##Starting awk program from here and creating 2 variables lines_from and till_lines here, where lines_from will have all line numbers which one wants to print from. till_lines is the value till lines one has to print.
BEGIN{                                           ##Starting BEGIN section of this program from here.
  num=split(lines_from,arr,",")                  ##Splitting lines_from into arr with delimiter of , here.
  for(i=1;i<=num;i++){                           ##Running a for loop from i=1 to till value of num here.
    line[arr[i]]                                 ##Creating array line with index of value of array arr with index of i here.
  }
}
FNR==NR{                                         ##Checking condition FNR==NR which will be TRUE when 1st time Input_file is being read.
  value[FNR]=$0                                  ##Creating value with index as FNR and its value is current line.
  next                                           ##next will skip all further statements from here.
}
(FNR in line){                                   ##Checking condition if current line number is coming in array then do following.
  print value[FNR] > "output_file"               ##Printing value with index of FNR into output_file
  j=""                                           ##Nullifying value of j here.
  while(++j<=till_lines){                        ##Running while loop from j=1 to till value of till_lines here.
    print value[FNR+j] > "output_file"           ##Printing value of array value with index of FNR+j and print output into output_file
  }
}
'  Input_file Input_file                         ##Mentioning Input_file names here.

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