Linux Shell script to change grep for a string, then comment out 2 lines above and 1 below the string found in the file

Question

Looking for some help on this task. I have tried several shell scripts to do this, but not sure I am approaching this problem right. I have a file that contains several blocks of data like this:

multipath {

wwid 360000970000195701574533030394530

alias DG_cln_DRPCU04_Oberon_IX_disk59

}

multipath {

wwid 360000970000195701574533030394531

alias DG_cln_DRPCU04_Oberon_IX_disk60
                }

multipath {

wwid 360000970000195701574533030394532

alias DG_cln_DRPCU04_Oberon_IX_disk61

}

multipath {

wwid 360000970000195701574533030394533

alias DG_cln_DRPCU04_Oberon_IX_disk62

}

multipath {

wwid 360000970000195701574533030394534

alias DG_cln_DRPCU04_Oberon_IX_disk63

}

multipath {

wwid 360000970000195701574533030394535

alias DG_cln_DRPCU04_Oberon_IX_disk6

}

multipath {

wwid 360000970000195701574533030394536

alias DG_cln_DRPCU04_Oberon_IX_disk64

}

I want to comment out only specific blocks. I want to change only the lines in the block that I have greped for.

Example:

grep -B 2 -A 1 DG_cln_DRPCU04_Oberon.

It would return every block that contains DG_cln_DRPCU04_Oberon. I then want to comment out that entire block of 4 lines, for each unique block that is returned. Is there an easy way to do this? Thanks for any pointers of suggestions on how to approach this problem.

Answer 1

You could do it in awk. Put the following script in a file and then call awk -v pattern=disk60 -f script_file data_file:

found { buf = buf "\n" $0 }
/multipath *\{/ { buf = $0; found = 1 }
!found { print }
$0 ~ pattern { matched = 1 }
/\}/ {
    if (matched) {
        gsub(/\n/, "\n#", buf);
        buf = "#" buf;
    }
    print buf "\n";
    buf = "";
    found = matched = 0;
}

This works as follows: If the line contains multipath and an opening curly bracket, start a new buffer, and set the variable found. As long as found is true, add the line to the buffer. If found is not true, print the line immediately, since we are outside of an interesting block. If the line matches the pattern you are looking for (disk60 in my example), set the variable matched. Finally, if the line contains a closing curly bracket, check whether matched is true. If so, comment out the lines in the buffer. Print the buffer and reset the variables.