How to get the final group of text between two patterns with sed or awk

Question

There are several answers on this site about how to capture text between two patterns and print out each group, but I am interested only in the last group. I am doing this on Mac, not Linux.

My output comes from echo "" | openssl s_client -showcerts -connect oidc.eks.us-east-1.amazonaws.com:443 2>&1 |\ sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p;/-END CERTIFICATE-/a\' and I want to grab the last cert, between -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- inclusive.

To generalize, in text like

start
a
b
c
end
start
d
e
f
end
start
g
h
i
end

how can I just get

start
g
h
i
end

The reason I need this is because I need to get the last cert in a chain to get its thumbprint via openssl x509 -fingerprint -noout to create an AWS OIDC provider programatically.

Always important to mention: [Is a /start/,/end/ range expression ever useful in awk?](https://stackoverflow.com/questions/23934486/is-a-start-end-range-expression-ever-useful-in-awk) — kvantour, Jan 24 '20 at 11:00

score 3 · Answer 1 · answered Jan 24 '20 at 05:12

3

$ awk '/start/{rec=""; f=1} f{rec=rec $0 ORS} /end/{f=0} END{printf "%s", rec}' file
start
g
h
i
end

answered Jan 24 '20 at 05:12

Ed Morton

188,023
17
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185

RavinderSingh13 · Accepted Answer · 2020-01-24T05:20:04.763

1

Could you please try following tac + awk solution.

tac Input_file | awk '/end/,/start/{print;if($0=="start"){exit}}' | tac

OR as per Ed sir's comments more concise solution will be:

tac Input_file | awk '/end/{f=1} f; /start/{exit}' | tac

Solution with detailed explanation:

tac Input_file |            ##Print Input_file in reverse style, from bottom to top.
awk '                       ##Starting awk program from here.
  /end/,/start/{            ##Printing from range starting from end to start here.
    print
    if($0=="start"){        ##Checking if current line is start then exit from awk program.
      exit
    }
  }
' |                         ##Sending awk output to next command. 
tac

Output will be as follows.

start
g
h
i
end

edited Jan 24 '20 at 05:20

answered Jan 24 '20 at 01:18

RavinderSingh13

130,504
14
57
93

The `awk` function does not work for me. I did this command and it just printed out the whole thing. (tail -r is the same as cat) echo "" | openssl s_client -showcerts -connect oidc.eks.us-east-1.amazonaws.com:443 2>&1 |\ sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p;/-END CERTIFICATE-/a\' | tail -r |\ awk '/-END CERTIFICATE-/,/-BEGIN CERTIFICATE-/{print;if($0=="start"){exit}}' | tail -r – swagrov Jan 24 '20 at 02:51
@swagrov, is it giving any error to you? Because when I tested it on bash it worked fine only – RavinderSingh13 Jan 24 '20 at 02:56
There is no error. I think the issue might be that the strings are `-----BEING CERTIFICATE-----` and `-----END CERTIFICATE-----`, not just `start` and `end`, so maybe that's the issue. I just tested your command with my example and it worked. Perhaps I should have explicitly use those strings. EDIT: I made a typo, see my final comment. – swagrov Jan 24 '20 at 03:01
@swagrov, what I am doing is to make calculation easy for awk I read reverse file so in spite of giving `/start/,/end/` give like `/end/,/start/` and it should fly then. Lemme know. – RavinderSingh13 Jan 24 '20 at 03:03
1

Your example works. It turns out I made a typo. Marking it as the answer. Thank you! – swagrov Jan 24 '20 at 03:04

score 1 · Answer 3 · answered Jan 24 '20 at 02:51

I got this functioning like this:

echo "" | openssl s_client -showcerts -connect oidc.eks.us-east-1.amazonaws.com:443 2>&1 |\
sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p;/-END CERTIFICATE-/a\' | tail -r |\
sed -n '1,/-BEGIN CERTIFICATE-/ p' | tail -r

tail -r is very useful for this.

KamilCuk · Answer 4 · 2020-01-24T01:22:48.073

0

Insert zero byte before each start. After that print last "line", where lines are separated by zero bytes.

sed 's/start/\x00&/` | tail -z -n1

edited Jan 24 '20 at 01:22

answered Jan 24 '20 at 01:16

KamilCuk

120,984
8
59
111

2

I should have mentioned that I am doing this on mac, and mac `tail` does not have the -z option like linux does. – swagrov Jan 24 '20 at 02:48

How to get the final group of text between two patterns with sed or awk

4 Answers4