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I want to remove a particular number of lines after the given pattern is matched.

Can anyone please tell me how that can be done using the sed command ?

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marked as duplicate by terdon, Anthon, slm, manatwork, jasonwryan Sep 26 '13 at 18:20

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2 Answers 2

sed -ne '/pattern/{n;n;n;n;d;}' -e p

Would delete the line matching the pattern and 4 lines after that.

If you don't want to delete the line matching the pattern itself:

sed -ne '/pattern/{p;n;n;n;n;d;}' -e p

Explanation: if the current line matches the pattern, [p]rint it, then get the [n]ext one, and [n]ext and [n]ext, and [n]ext and [d]iscard it. Because of the [d]iscard, the [p]rint command is not run in that case. It is run for every other line. -n disables automatic printing (which would print almost everything) and thus implies the use of -e p, which makes sure the resulting lines are printed.


$ seq 8 | sed -ne '/2/{p;n;n;n;n;d;}' -e p

To be able to specify the number of lines as a number, it would be easier with awk:

awk 'n>0 {n--;next}; /pattern/{n=4}; 1'

(note that in all those solutions, the pattern is not looked for in the lines that are being skipped).

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yes I would like to delete the lines after the pattern matching . Can you provide easy understanding of sed command tutorial ? –  user2720323 Sep 26 '13 at 10:57
Could you please explain the terms used in 'sed -ne '/pattern/{p;n;n;n;n;d;}' -e p' comamnd –  user2720323 Sep 26 '13 at 11:09

Two step, assuming bash. Assuming 2 lines to be removed after the lines containing "pattern". Note: The line which contains pattern is NOT removed, but 2 lines after that are removed.

To remove N lines, change A2 -> AN in grep arguments

grep -n -A2 pattern inputFile | grep -Ev pattern | sed 's/^\([0-9]*\)-.*/\1/g' > linesToRemove

while read p; do sed -i "${p}d" inputFile; done < linesToRemove

If you also want to delete the line containing pattern, change grep command to

grep -n -A2 pattern inputFile | sed 's/^\([0-9]*\)[-:].*/\1/g' > linesToRemove

Explanation: First command finds out line numbers of lines to be deleted. Second command deletes these lines one after another. Use to learn more or just man grep

If your sed does not have -i option, read

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