Fill in rows missing row labels for repeated values - awk

Question

I have the following input:
printf "Name\tArea\tNumber\tA\tB\tC\n\t\t\tA\tB\tC\n\t\t\tA\tB\tC\n"
Name Area Number A B C
A B C
A B C
If first 3 columns are blank,
I want to print the previous 3 columns along with the data of the new line,
else print the line as is. Output should look like this:
printf "Name\tArea\tNumber\tA\tB\tC\nName\tArea\tNumber\tA\tB\tC\nName\tArea\tNumber\tA\tB\tC\n"
Name Area Number A B C
Name Area Number A B C
Name Area Number A B C

Answer 1

My interpretation of the question is that fields 1 to 3 can appear anywhere in the file, with values possibly different from the ones they had previously. So the idea would be to reproduce the last fields 1 to 3 seen so far, so that the input:
Name Area Number A B C
A B D
F G T
Nam Zig BBA U Z x
A B D
would produce the output:
Name Area Number A B C
Name Area Number A B D
Name Area Number F G T
Nam Zig BBA U Z x
Nam Zig BBA A B D
So I propose:
awk 'BEGIN {FS=OFS="\t"; hd1=hd2=hd3=""} $1=="" {$1=hd1;$2=hd2;$3=hd3; print; next} {hd1=$1;hd2=$2;hd3=$3; print}' yourfile
ok, I only checked the non-nullity of $1, but we could easily adapt to add only the missing fields.

Answer 2

I would solve this as a fixed width problem. A GNU awk solution:
$ awk '$1~/^ +$/{sub($1,h)}{h=$1}1' FIELDWIDTHS=23 file
Name Area Number A B C
Name Area Number A B D
Name Area Number F G T
Nam Zig BBA U Z x
Nam Zig BBA A B D
Just change the FIELDWIDTHS variable to match your data as needed.
The other more verbose approach is to iterate over each of the fields that could be missing:
$ awk '{for(i=1;i<=c;i++)if($i=="")$i=h[i]}{for(i=1;i<=c;i++)h[i]=$i}1' c=3 FS='\t' OFS='\t' file
Name Area Number A B C
Name Area Number A B D
Name Area Number F G T
Nam Zig BBA U Z x
Nam Zig BBA A B D
Just change c to the value of missing columns you want to check.