Example:
>"one"
>"two"
>"three"
>"title"
>12 23 14
>...
I want to remove all lines at the beginning until I reach the one in which NF==3 (awk), but the line named "title", and just once at the beginning of the file, not repeatedly.
Thank you
Expected output:
>"title"
>12 23 14
>...
The way to do this is by using awk as you already suggested. As you say, you want to print the lines starting from the first occurrence where you have 3 fields, this can easily be done by setting a print flag (let's call it p)'
awk '(NF==3){p=1};p' file
This will print everything starting from the first line with 3 fields.
However, you would also like to print the line which contains the string "title". This can be done by matching this string :
awk '/title/{print}(NF==3){p=1};p' file
The problem with this is that it is possible that the word 'title' will be printed twice when your file looks like
a < not printed
title < printed
a b c < printed
title < printed twice
e f g < printed
h < printed
So you have to be a bit more careful here with your logic and place the check together with the check when to print:
awk '(NF==3){p=1};(p || /title/)' file
This again is not robust because you might have a file like:
a < not printed
title 1 < printed
b < not printed
title 2 < printed
a b c < printed
h < printed
and you only want "title 2" to be printed:
awk '/title/{s=$0}(NF==3){p=1;print s};p' file
If the "title" just refers to the line before the first line with 3 fields, then you do
awk '(NF==3){p=1;print s};p;{s=$0}' file
or for a minor speedup:
awk '(NF==3){p=1;print s};p{print; next}{s=$0}' file