CODEWITHSUNDEEP
bashawk
ehime
ehime

Reputation: 8375

How to reverse everything after the second line with AWK

I'm looking for a way to ignore the first two lines of a file, and flip the ips/dns' of everything after the second line. Please note that I sed remove first line (which is a header).

bash-4.4$ less test
  1 #remove
  2 #comment 1
  3 #comment 2
  4 foo 127.0.0.1
  5 bar 127.0.0.1

the results I am looking for are

bash-4.4$ less test-fixed
  1 #comment 1
  2 #comment 2
  3 127.0.0.1 foo
  4 127.0.0.1 bar

the command pipe I've been trying is:

FILE=/tmp/test ; sed '1d' $FILE | awk 'NR>2 { t = $1; $1 = $2; $2 = t; print; } ' >| /tmp/test-fixed

obviously NR>2 ordinal number of the current record and skips to line 3 so I'm thinking I need an iteration loop to print them but not operate until N3 is reached? Not sure...

Upvotes: 4

Views: 228

Answers (3)

karakfa
karakfa

Reputation: 67467

with line numbers

$ awk 'NR==1 {next} 
       NR>3  {t=$3; $3=$2; $2=t} 
             {print NR-1,$2,$3}' file

1 #comment 1
2 #comment 2
3 127.0.0.1 foo
4 127.0.0.1 bar

or golfed version

$ awk 'NR>3{t=$3;$3=$2;$2=t} --$1' file

Upvotes: 2

MiniMax
MiniMax

Reputation: 1093

awk 'NR > 1 && NR <= 3; NR > 3 {print $2, $1}' input.txt

Output

#comment 1
#comment 2
127.0.0.1 foo
127.0.0.1 bar

Upvotes: 3

anubhava
anubhava

Reputation: 784998

You can use awk like this:

awk 'NR>3{s=$NF; $NF = $(NF-1); $(NF-1) = s} 1' file

1 #remove
2 #comment 1
3 #comment 2
4 127.0.0.1 foo
5 127.0.0.1 bar

Upvotes: 4

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