BASH List Search Awk

Question

I'm very new to scripting and trying to work something out in bash. I have a data file filled with information that looks like this:

2   aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1   
4   aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1]   1 
8   aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1   
10  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1   
12  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaaa.aaa    11111   aaaa    1111    [1] 1   
14  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1   
16  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaaa.aaa    11111   aaaa    1111    [1] 1   
18  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1   
20  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaaa.aaa    11111   aaaa    1111    [1] 1   
24  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaaa.aaa    11111   aaaa    1111    [1] 1   
26  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaaa.aaa    11111   aaaa    1111    [1] 1   
28  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1   
30  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1   
32  aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaaa.aaa    11111   aaaa    1111    [1] 1   

Where the *a's represent various letters and the 1's represent various numbers.

The lists are all supposed to go down vertically from 2 to 32 counting by 2's, however a lot of the lists are missing a couple components, such as the one I posted above which is missing 6 and 22. What I am trying to do is write a script that would go through and check to see if each number is there, and if not, add a line with the number at the front and nothing else trailing, so you'd have:

2   aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    
[1] 1   
4   aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1]   1 
6

8   aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aa11_1.aaa aaaa.aaa 11111   aaaa    1111    [1] 1      
...

From what I have read I believe the AWK function will be the most likely to succeed, however I'm not sure how to make it work. Thanks!

Answer 1

This awk is based on the output index range of 2-32 (by two) entries:

awk '{a[$1]=$0} END {for(i=2;i<=32;i+=2) print (i in a ? a[i] : i)}' data

The breakdown:

• Store all the existing lines in an array by their index
• At the END, walk all known indexes (2-32) and either print the line, or the missing index