CODEWITHSUNDEEP
unixsedawkgawk
user1407199
user1407199

Reputation: 183

Delete all lines after a string but the last few

I have file which contains some lines and some numbers. I want to delete all the lines after particular string, let us say the string is 'angles'. I want to delete all the lines after angles, I can do this using sed command as follows: 

sed -n '/angles/q;p' input file

My question is, I want to delete all the lines after angles but want to retain the last four lines? How can I do this in sed?

Upvotes: 1

Views: 455

Answers (5)

glenn jackman
glenn jackman

Reputation: 247012

I'm going to assume the string you're looking for may occur more than once, and you only want up to the first one. If that's true, reversing the file isn't the best strategy.

{ sed '/angles/q' file; tail -4 file; } > result

Upvotes: 0

Ed Morton
Ed Morton

Reputation: 204015

awk -v size=$(wc -l < file) '
    /angles/       { skip=1 }
    NR >= (size-4) { skip=0 }
    !skip
' file

Upvotes: 0

potong
potong

Reputation: 58483

This might work for you (GNU sed):

sed '1,/angles/b;:a;$!{N;s/\n/&/4;Ta;D}' file

Print out all the lines from the first till encountering the string angles. Then make a moving window of four lines and print them at end of file.

Upvotes: 1

Vijay
Vijay

Reputation: 67291

In awk :

awk '{
     if(p!=1)print;
     else{a[NR]=$0}
     if($0~/angles/)p=1
     }
     END{
     for(i=NR-3;i<=NR;i++)print a[i]
     }' your_file

Tested below:

> cat temp
wbj
ergthet
gheheh
wergergkn   angles gerg
er
ergnmer
rgnerk
1
2
3
4
> awk '{if(p!=1)print;else{a[NR]=$0};if($0~/angles/)p=1}END{for(i=NR-3;i<=NR;i++)print a[i]}' temp
wbj
ergthet
gheheh
wergergkn   angles gerg
1
2
3
4
>

Upvotes: 0

devnull
devnull

Reputation: 123608

The following should work for you:

tac inputfile | sed '5,/angles/d' | tac

Explanation: Reverse the file, keep first 4 lines and delete everything until the desired pattern is encounterd. Reverse the result.

Upvotes: 1

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