It should work, to learn this stuff is to read about it and find it out yourself, so try it out.

The idea of the script, to replace the 3th line with the 9th, is:

1. print all lines untill line 3-1 (2nd line)
2. place the 4th line untill line 9-1 (8th line) before the 3th line in the variable s separated by a newline
3. print the 9th line
4. print the variable s
5. print other lines after the 9th line

Code:

#!/bin/sh
 
line=3
line1=10

awk -v var="$line" -v var1="$line1" 'NR==var {
  s=$0
  for(i=var+1;i<var1;i++){
    getline;s=$0"\n"s
  }
  getline;print;print s
  next
}1' file

Explanation of the code:

Code:

awk -v var="$line" -v var1="$line1"

Place the shellvariables in awk variables.

Code:

NR==var

If the linenumber is equal to 3 execute the commands between the curly brackets {}

Code:

s=$0

Place the current line in the variable s

Code:

  for(i=var+1;i<var1;i++){
    getline;s=$0"\n"s
  }

Loop through the lines 4 till 8 and place the lines before the 3th line separated by a newline.

Code:

  getline;print;print s
  next

Read the next line (9th line), print the line, print the variable s and read the next line

Code:

1

awk evaluates the 1 as true and the prints the entire line by default, an equivalent of {print}.


Regards