Use sed to delete a matched regexp and the line (or two) underneath it

Question

OK I found this question:

http://stackoverflow.com/questions/876446/how-do-i-delete-a-matching-line-the-line-above-and-the-one-below-it-using-sed

and just spent the last hour trying to write something that will match a string and delete the line containing the string and the line beneath it (or a variant - delete 2 lines beneath it).

I feel I'm now typing random strings. Please somebody help me.

Answer 1

If I've understood that correctly, to delete match line and one line after

/matchstr/{N;d;}

Match line and two lines after

/matchstr/{N;N;d;}

• N brings in the next line
• d - deletes the resulting single line

Answer 2

you can use awk. eg search for the word "two" and skip 2 lines after it

$ cat file
one
two
three
four
five
six
seven
eight
$ awk -vnum=2 '/two/{for(i=0;i<=num;i++)getline}1' file
one
five
six
seven
eight