a little tricky.. adding comment but in specific case

[bfman]

Hi All,

So I've been trying to do this for a while now with not much luck as I'm a newbie to bash scripting.

Example of file:

line above it 01
this is a testline for a pattern
line above it 02
this is the second testline
line above it 03
that is the second testline
line above it 04
this is the third testline
line above it 05
that is the third testline

What I want is to put comment (#) at the beginning of line that contains the string "second" and starts with "that" AND I also want to put a comment (#) on the line right above it.
So in the example given above, it would be this line:

that is the second testline

And the line right above it would be:

line above it 03

I tried doing different kinds of for and while loops with sed etc. but can't get this working. Can someone please help?

Thank you!

[atreyu]

I'd do this with bash's built-in arrays. Assume your file contents are in a file named "test1.txt".

#!/bin/bash
file=test1.txt
declare -i n
declare -a lines
n=0
while read line; do
#  echo Line $n: $line
  echo $line|grep -q '^that .*second'
  if [ $? -eq 0 ]; then
    lines[$n]="#${line}"
    lines[$(($n - 1))]="#${lines[$(($n - 1))]}"
  else
    lines[$n]="$line"
  fi
  let n+=1
done < $file

#echo -e "Number of lines: ${#lines[*]}\n"
for (( i=0; i<${#lines[*]}; i++ )); do
  echo "${lines[$i]}"
done